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	$76.54	11.756%	$85.538	$85.54	$85.55	$85.50
Purchase #2	$147.56	12.171%	$165.5195	$165.52	$165.50	$165.50
Purchase #3	$93.39	7.478%	$100.3737	$100.37	$100.35	$100.40
Purchase #4	$146.71	12.660%	$165.2835	$165.28	$165.30	$165.30
Purchase #5	$187.76	5.177%	$197.4803	$197.48	$197.50	$197.50
Purchase #6	$175.89	9.199%	$192.0701	$192.07	$192.05	$192.10
Purchase #7	$66.66	10.378%	$73.578	$73.58	$73.60	$73.60
7 purchase totals =	$894.51		$979.8431	$979.84	$979.85	$979.90