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	$39.83	13.268%	$45.1146	$45.11	$45.10	$45.10
Purchase #2	$168.26	13.672%	$191.2645	$191.26	$191.25	$191.30
Purchase #3	$120.79	7.642%	$130.0208	$130.02	$130.00	$130.00
Purchase #4	$72.72	7.498%	$78.1725	$78.17	$78.15	$78.20
Purchase #5	$155.72	8.295%	$168.637	$168.64	$168.65	$168.60
Purchase #6	$5.68	13.165%	$6.4278	$6.43	$6.45	$6.40
Purchase #7	$64.53	3.266%	$66.6375	$66.64	$66.65	$66.60
7 purchase totals =	$627.53		$686.2747	$686.27	$686.25	$686.20