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	$196.65	7.141%	$210.6928	$210.69	$210.70	$210.70
Purchase #2	$52.43	12.422%	$58.9429	$58.94	$58.95	$58.90
Purchase #3	$99.74	4.121%	$103.8503	$103.85	$103.85	$103.90
Purchase #4	$234.94	6.363%	$249.8892	$249.89	$249.90	$249.90
Purchase #5	$28.84	3.848%	$29.9498	$29.95	$29.95	$29.90
Purchase #6	$51.82	11.393%	$57.7239	$57.72	$57.70	$57.70
Purchase #7	$195.41	13.718%	$222.2163	$222.22	$222.20	$222.20
7 purchase totals =	$859.83		$933.2652	$933.26	$933.25	$933.20