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	$133.91	9.481%	$146.606	$146.61	$146.60	$146.60
Purchase #2	$130.62	8.685%	$141.9643	$141.96	$141.95	$142.00
Purchase #3	$139.73	5.624%	$147.5884	$147.59	$147.60	$147.60
Purchase #4	$85.61	4.802%	$89.721	$89.72	$89.70	$89.70
Purchase #5	$159.36	9.857%	$175.0681	$175.07	$175.05	$175.10
Purchase #6	$111.93	13.217%	$126.7238	$126.72	$126.70	$126.70
Purchase #7	$192.80	9.549%	$211.2105	$211.21	$211.20	$211.20
7 purchase totals =	$953.96		$1,038.8821	$1,038.88	$1,038.80	$1,038.90