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	$144.53	10.178%	$159.2403	$159.24	$159.25	$159.20
Purchase #2	$55.50	10.767%	$61.4757	$61.48	$61.50	$61.50
Purchase #3	$136.46	11.468%	$152.1092	$152.11	$152.10	$152.10
Purchase #4	$73.38	12.208%	$82.3382	$82.34	$82.35	$82.30
Purchase #5	$159.34	9.254%	$174.0853	$174.09	$174.10	$174.10
Purchase #6	$64.54	11.138%	$71.7285	$71.73	$71.75	$71.70
Purchase #7	$76.91	5.660%	$81.2631	$81.26	$81.25	$81.30
7 purchase totals =	$710.66		$782.2403	$782.25	$782.30	$782.20