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	$148.82	12.817%	$167.8943	$167.89	$167.90	$167.90
Purchase #2	$246.67	3.636%	$255.6389	$255.64	$255.65	$255.60
Purchase #3	$125.29	10.157%	$138.0157	$138.02	$138.00	$138.00
Purchase #4	$205.52	5.511%	$216.8462	$216.85	$216.85	$216.80
Purchase #5	$66.66	6.404%	$70.9289	$70.93	$70.95	$70.90
Purchase #6	$244.95	3.787%	$254.2263	$254.23	$254.25	$254.20
Purchase #7	$67.54	12.765%	$76.1615	$76.16	$76.15	$76.20
7 purchase totals =	$1,105.45		$1,179.7118	$1,179.72	$1,179.75	$1,179.60