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	$71.34	9.483%	$78.1052	$78.11	$78.10	$78.10
Purchase #2	$27.54	6.550%	$29.3439	$29.34	$29.35	$29.30
Purchase #3	$113.54	9.581%	$124.4183	$124.42	$124.40	$124.40
Purchase #4	$198.74	11.679%	$221.9508	$221.95	$221.95	$222.00
Purchase #5	$141.27	4.753%	$147.9846	$147.98	$148.00	$148.00
Purchase #6	$241.78	13.723%	$274.9595	$274.96	$274.95	$275.00
Purchase #7	$216.34	11.175%	$240.516	$240.52	$240.50	$240.50
7 purchase totals =	$1,010.55		$1,117.2783	$1,117.28	$1,117.25	$1,117.30