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	$206.53	8.289%	$223.6493	$223.65	$223.65	$223.60
Purchase #2	$196.38	13.670%	$223.2251	$223.23	$223.25	$223.20
Purchase #3	$57.72	3.547%	$59.7673	$59.77	$59.75	$59.80
Purchase #4	$25.88	6.467%	$27.5537	$27.55	$27.55	$27.60
Purchase #5	$159.84	10.641%	$176.8486	$176.85	$176.85	$176.80
Purchase #6	$87.95	13.743%	$100.037	$100.04	$100.05	$100.00
Purchase #7	$191.80	10.377%	$211.7031	$211.70	$211.70	$211.70
7 purchase totals =	$926.10		$1,022.7841	$1,022.79	$1,022.80	$1,022.70