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	$67.74	7.256%	$72.6552	$72.66	$72.65	$72.70
Purchase #2	$229.63	11.237%	$255.4335	$255.43	$255.45	$255.40
Purchase #3	$39.56	4.865%	$41.4846	$41.48	$41.50	$41.50
Purchase #4	$155.33	4.574%	$162.4348	$162.43	$162.45	$162.40
Purchase #5	$78.32	9.449%	$85.7205	$85.72	$85.70	$85.70
Purchase #6	$233.28	9.228%	$254.8071	$254.81	$254.80	$254.80
Purchase #7	$52.68	7.254%	$56.5014	$56.50	$56.50	$56.50
7 purchase totals =	$856.54		$929.0371	$929.03	$929.05	$929.00