Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.73	10.700%	$211.1381	$211.14	$211.15	$211.10
Purchase #2	$191.58	7.836%	$206.5922	$206.59	$206.60	$206.60
Purchase #3	$132.36	7.487%	$142.2698	$142.27	$142.25	$142.30
Purchase #4	$109.60	12.325%	$123.1082	$123.11	$123.10	$123.10
Purchase #5	$118.35	12.118%	$132.6917	$132.69	$132.70	$132.70
Purchase #6	$231.81	6.779%	$247.5244	$247.52	$247.50	$247.50
Purchase #7	$105.72	5.214%	$111.2322	$111.23	$111.25	$111.20
7 purchase totals =	$1,080.15		$1,174.5566	$1,174.55	$1,174.55	$1,174.50