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	$75.45	10.764%	$83.5714	$83.57	$83.55	$83.60
Purchase #2	$125.63	9.164%	$137.1427	$137.14	$137.15	$137.10
Purchase #3	$64.87	9.431%	$70.9879	$70.99	$71.00	$71.00
Purchase #4	$99.54	12.346%	$111.8292	$111.83	$111.85	$111.80
Purchase #5	$156.66	11.765%	$175.091	$175.09	$175.10	$175.10
Purchase #6	$165.65	4.440%	$173.0049	$173.00	$173.00	$173.00
Purchase #7	$244.77	13.713%	$278.3353	$278.34	$278.35	$278.30
7 purchase totals =	$932.57		$1,029.9624	$1,029.96	$1,030.00	$1,029.90