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	$219.70	11.554%	$245.0841	$245.08	$245.10	$245.10
Purchase #2	$15.96	13.651%	$18.1387	$18.14	$18.15	$18.10
Purchase #3	$160.62	11.199%	$178.6078	$178.61	$178.60	$178.60
Purchase #4	$48.81	6.756%	$52.1076	$52.11	$52.10	$52.10
Purchase #5	$58.55	11.399%	$65.2241	$65.22	$65.20	$65.20
Purchase #6	$106.62	4.518%	$111.4371	$111.44	$111.45	$111.40
Purchase #7	$142.94	5.200%	$150.3729	$150.37	$150.35	$150.40
7 purchase totals =	$753.20		$820.9723	$820.97	$820.95	$820.90