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	$226.40	13.234%	$256.3618	$256.36	$256.35	$256.40
Purchase #2	$50.82	5.769%	$53.7518	$53.75	$53.75	$53.80
Purchase #3	$71.99	6.162%	$76.426	$76.43	$76.45	$76.40
Purchase #4	$185.98	11.764%	$207.8587	$207.86	$207.85	$207.90
Purchase #5	$33.84	13.404%	$38.3759	$38.38	$38.40	$38.40
Purchase #6	$208.98	10.672%	$231.2823	$231.28	$231.30	$231.30
Purchase #7	$37.65	7.607%	$40.514	$40.51	$40.50	$40.50
7 purchase totals =	$815.66		$904.5705	$904.57	$904.60	$904.70