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	$67.35	6.240%	$71.5526	$71.55	$71.55	$71.60
Purchase #2	$137.60	8.534%	$149.3428	$149.34	$149.35	$149.30
Purchase #3	$33.64	9.446%	$36.8176	$36.82	$36.80	$36.80
Purchase #4	$222.61	3.236%	$229.8137	$229.81	$229.80	$229.80
Purchase #5	$58.55	5.140%	$61.5595	$61.56	$61.55	$61.60
Purchase #6	$204.92	6.548%	$218.3382	$218.34	$218.35	$218.30
Purchase #7	$82.92	3.155%	$85.5361	$85.54	$85.55	$85.50
7 purchase totals =	$807.59		$852.9605	$852.96	$852.95	$852.90