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	$125.83	9.472%	$137.7486	$137.75	$137.75	$137.70
Purchase #2	$168.79	9.641%	$185.063	$185.06	$185.05	$185.10
Purchase #3	$99.34	13.168%	$112.4211	$112.42	$112.40	$112.40
Purchase #4	$216.91	7.823%	$233.8789	$233.88	$233.90	$233.90
Purchase #5	$100.89	7.515%	$108.4719	$108.47	$108.45	$108.50
Purchase #6	$20.69	11.810%	$23.1335	$23.13	$23.15	$23.10
Purchase #7	$236.45	9.838%	$259.712	$259.71	$259.70	$259.70
7 purchase totals =	$968.90		$1,060.4290	$1,060.42	$1,060.40	$1,060.40