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	$87.68	12.153%	$98.3358	$98.34	$98.35	$98.30
Purchase #2	$126.45	12.710%	$142.5218	$142.52	$142.50	$142.50
Purchase #3	$209.89	5.431%	$221.2891	$221.29	$221.30	$221.30
Purchase #4	$165.79	4.790%	$173.7313	$173.73	$173.75	$173.70
Purchase #5	$221.51	6.594%	$236.1164	$236.12	$236.10	$236.10
Purchase #6	$146.53	9.419%	$160.3317	$160.33	$160.35	$160.30
Purchase #7	$53.54	11.740%	$59.8256	$59.83	$59.85	$59.80
7 purchase totals =	$1,011.39		$1,092.1517	$1,092.16	$1,092.20	$1,092.00