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	$153.28	10.224%	$168.9513	$168.95	$168.95	$169.00
Purchase #2	$74.91	12.232%	$84.073	$84.07	$84.05	$84.10
Purchase #3	$250.71	8.143%	$271.1253	$271.13	$271.15	$271.10
Purchase #4	$198.89	9.507%	$217.7985	$217.80	$217.80	$217.80
Purchase #5	$51.89	11.231%	$57.7178	$57.72	$57.70	$57.70
Purchase #6	$86.31	3.568%	$89.3895	$89.39	$89.40	$89.40
Purchase #7	$28.79	12.268%	$32.322	$32.32	$32.30	$32.30
7 purchase totals =	$844.78		$921.3774	$921.38	$921.35	$921.40