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	$243.82	8.487%	$264.513	$264.51	$264.50	$264.50
Purchase #2	$72.58	8.701%	$78.8952	$78.90	$78.90	$78.90
Purchase #3	$117.81	13.439%	$133.6425	$133.64	$133.65	$133.60
Purchase #4	$149.75	10.545%	$165.5411	$165.54	$165.55	$165.50
Purchase #5	$111.67	10.732%	$123.6544	$123.65	$123.65	$123.70
Purchase #6	$87.77	11.395%	$97.7714	$97.77	$97.75	$97.80
Purchase #7	$235.46	12.760%	$265.5047	$265.50	$265.50	$265.50
7 purchase totals =	$1,018.86		$1,129.5223	$1,129.51	$1,129.50	$1,129.50