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	$232.65	13.191%	$263.3389	$263.34	$263.35	$263.30
Purchase #2	$211.68	12.532%	$238.2077	$238.21	$238.20	$238.20
Purchase #3	$56.84	12.706%	$64.0621	$64.06	$64.05	$64.10
Purchase #4	$241.53	6.357%	$256.8841	$256.88	$256.90	$256.90
Purchase #5	$64.54	9.762%	$70.8404	$70.84	$70.85	$70.80
Purchase #6	$69.65	9.539%	$76.2939	$76.29	$76.30	$76.30
Purchase #7	$104.99	6.516%	$111.8311	$111.83	$111.85	$111.80
7 purchase totals =	$981.88		$1,081.4582	$1,081.45	$1,081.50	$1,081.40