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	$47.58	12.523%	$53.5384	$53.54	$53.55	$53.50
Purchase #2	$47.70	13.712%	$54.2406	$54.24	$54.25	$54.20
Purchase #3	$197.87	11.140%	$219.9127	$219.91	$219.90	$219.90
Purchase #4	$105.37	3.733%	$109.3035	$109.30	$109.30	$109.30
Purchase #5	$250.88	10.845%	$278.0879	$278.09	$278.10	$278.10
Purchase #6	$218.77	10.787%	$242.3687	$242.37	$242.35	$242.40
Purchase #7	$64.53	5.216%	$67.8959	$67.90	$67.90	$67.90
7 purchase totals =	$932.70		$1,025.3477	$1,025.35	$1,025.35	$1,025.30