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	$172.51	13.498%	$195.7954	$195.80	$195.80	$195.80
Purchase #2	$53.31	3.130%	$54.9786	$54.98	$55.00	$55.00
Purchase #3	$92.71	11.237%	$103.1278	$103.13	$103.15	$103.10
Purchase #4	$137.95	3.144%	$142.2871	$142.29	$142.30	$142.30
Purchase #5	$112.35	10.401%	$124.0355	$124.04	$124.05	$124.00
Purchase #6	$51.34	13.634%	$58.3397	$58.34	$58.35	$58.30
Purchase #7	$98.45	7.183%	$105.5217	$105.52	$105.50	$105.50
7 purchase totals =	$718.62		$784.0858	$784.10	$784.15	$784.00