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	$42.81	5.293%	$45.0759	$45.08	$45.10	$45.10
Purchase #2	$204.38	10.455%	$225.7479	$225.75	$225.75	$225.70
Purchase #3	$196.59	12.792%	$221.7378	$221.74	$221.75	$221.70
Purchase #4	$209.42	13.200%	$237.0634	$237.06	$237.05	$237.10
Purchase #5	$141.98	7.300%	$152.3445	$152.34	$152.35	$152.30
Purchase #6	$129.37	13.582%	$146.941	$146.94	$146.95	$146.90
Purchase #7	$200.38	12.330%	$225.0869	$225.09	$225.10	$225.10
7 purchase totals =	$1,124.93		$1,253.9974	$1,254.00	$1,254.05	$1,253.90