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	$150.43	12.443%	$169.148	$169.15	$169.15	$169.10
Purchase #2	$229.91	12.446%	$258.5246	$258.52	$258.50	$258.50
Purchase #3	$154.63	11.605%	$172.5748	$172.57	$172.55	$172.60
Purchase #4	$62.25	3.442%	$64.3926	$64.39	$64.40	$64.40
Purchase #5	$127.25	8.405%	$137.9454	$137.95	$137.95	$137.90
Purchase #6	$56.98	7.426%	$61.2113	$61.21	$61.20	$61.20
Purchase #7	$191.85	3.376%	$198.3269	$198.33	$198.35	$198.30
7 purchase totals =	$973.30		$1,062.1236	$1,062.12	$1,062.10	$1,062.00