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	$152.37	10.191%	$167.898	$167.90	$167.90	$167.90
Purchase #2	$43.40	10.764%	$48.0716	$48.07	$48.05	$48.10
Purchase #3	$34.63	7.315%	$37.1632	$37.16	$37.15	$37.20
Purchase #4	$112.80	13.584%	$128.1228	$128.12	$128.10	$128.10
Purchase #5	$240.46	7.338%	$258.105	$258.11	$258.10	$258.10
Purchase #6	$232.51	6.464%	$247.5394	$247.54	$247.55	$247.50
Purchase #7	$53.29	5.149%	$56.0339	$56.03	$56.05	$56.00
7 purchase totals =	$869.46		$942.9339	$942.93	$942.90	$942.90