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	$235.39	7.720%	$253.5621	$253.56	$253.55	$253.60
Purchase #2	$130.38	10.515%	$144.0895	$144.09	$144.10	$144.10
Purchase #3	$216.32	3.466%	$223.8177	$223.82	$223.80	$223.80
Purchase #4	$214.36	13.519%	$243.3393	$243.34	$243.35	$243.30
Purchase #5	$86.56	3.697%	$89.7601	$89.76	$89.75	$89.80
Purchase #6	$120.59	3.442%	$124.7407	$124.74	$124.75	$124.70
Purchase #7	$236.65	8.273%	$256.2281	$256.23	$256.25	$256.20
7 purchase totals =	$1,240.25		$1,335.5375	$1,335.54	$1,335.55	$1,335.50