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	$37.88	10.515%	$41.8631	$41.86	$41.85	$41.90
Purchase #2	$145.55	9.609%	$159.5359	$159.54	$159.55	$159.50
Purchase #3	$54.77	3.339%	$56.5988	$56.60	$56.60	$56.60
Purchase #4	$197.71	13.469%	$224.3396	$224.34	$224.35	$224.30
Purchase #5	$229.81	11.381%	$255.9647	$255.96	$255.95	$256.00
Purchase #6	$135.43	8.109%	$146.412	$146.41	$146.40	$146.40
Purchase #7	$236.81	11.153%	$263.2214	$263.22	$263.20	$263.20
7 purchase totals =	$1,037.96		$1,147.9355	$1,147.93	$1,147.90	$1,147.90