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	$60.40	7.481%	$64.9185	$64.92	$64.90	$64.90
Purchase #2	$157.75	11.274%	$175.5347	$175.53	$175.55	$175.50
Purchase #3	$174.70	12.476%	$196.4956	$196.50	$196.50	$196.50
Purchase #4	$78.64	3.753%	$81.5914	$81.59	$81.60	$81.60
Purchase #5	$36.89	11.331%	$41.07	$41.07	$41.05	$41.10
Purchase #6	$208.25	13.695%	$236.7698	$236.77	$236.75	$236.80
Purchase #7	$224.87	7.633%	$242.0343	$242.03	$242.05	$242.00
7 purchase totals =	$941.50		$1,038.4143	$1,038.41	$1,038.40	$1,038.40