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	$211.59	5.770%	$223.7987	$223.80	$223.80	$223.80
Purchase #2	$131.85	4.377%	$137.6211	$137.62	$137.60	$137.60
Purchase #3	$228.99	11.272%	$254.8018	$254.80	$254.80	$254.80
Purchase #4	$111.82	11.459%	$124.6335	$124.63	$124.65	$124.60
Purchase #5	$47.56	9.672%	$52.16	$52.16	$52.15	$52.20
Purchase #6	$232.66	11.682%	$259.8393	$259.84	$259.85	$259.80
Purchase #7	$109.51	12.610%	$123.3192	$123.32	$123.30	$123.30
7 purchase totals =	$1,073.98		$1,176.1736	$1,176.17	$1,176.15	$1,176.10