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	$164.26	9.701%	$180.1949	$180.19	$180.20	$180.20
Purchase #2	$126.80	3.314%	$131.0022	$131.00	$131.00	$131.00
Purchase #3	$67.33	13.736%	$76.5784	$76.58	$76.60	$76.60
Purchase #4	$213.62	7.370%	$229.3638	$229.36	$229.35	$229.40
Purchase #5	$54.30	9.233%	$59.3135	$59.31	$59.30	$59.30
Purchase #6	$143.80	5.392%	$151.5537	$151.55	$151.55	$151.60
Purchase #7	$230.41	6.288%	$244.8982	$244.90	$244.90	$244.90
7 purchase totals =	$1,000.52		$1,072.9047	$1,072.89	$1,072.90	$1,073.00