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	$98.89	6.344%	$105.1636	$105.16	$105.15	$105.20
Purchase #2	$95.85	9.716%	$105.1628	$105.16	$105.15	$105.20
Purchase #3	$118.86	12.683%	$133.935	$133.94	$133.95	$133.90
Purchase #4	$15.76	6.613%	$16.8022	$16.80	$16.80	$16.80
Purchase #5	$140.91	8.771%	$153.2692	$153.27	$153.25	$153.30
Purchase #6	$7.34	7.293%	$7.8753	$7.88	$7.90	$7.90
Purchase #7	$78.77	9.148%	$85.9759	$85.98	$86.00	$86.00
7 purchase totals =	$556.38		$608.1840	$608.19	$608.20	$608.30