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	$168.46	11.676%	$188.1294	$188.13	$188.15	$188.10
Purchase #2	$51.83	11.472%	$57.7759	$57.78	$57.80	$57.80
Purchase #3	$228.82	4.518%	$239.1581	$239.16	$239.15	$239.20
Purchase #4	$135.72	11.666%	$151.5531	$151.55	$151.55	$151.60
Purchase #5	$183.64	5.563%	$193.8559	$193.86	$193.85	$193.90
Purchase #6	$159.94	6.344%	$170.0866	$170.09	$170.10	$170.10
Purchase #7	$43.81	4.760%	$45.8954	$45.90	$45.90	$45.90
7 purchase totals =	$972.22		$1,046.4544	$1,046.47	$1,046.50	$1,046.60