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	$110.73	13.379%	$125.5446	$125.54	$125.55	$125.50
Purchase #2	$146.65	3.452%	$151.7124	$151.71	$151.70	$151.70
Purchase #3	$214.34	8.371%	$232.2824	$232.28	$232.30	$232.30
Purchase #4	$100.84	4.353%	$105.2296	$105.23	$105.25	$105.20
Purchase #5	$9.94	13.743%	$11.3061	$11.31	$11.30	$11.30
Purchase #6	$181.41	8.215%	$196.3128	$196.31	$196.30	$196.30
Purchase #7	$130.38	6.856%	$139.3189	$139.32	$139.30	$139.30
7 purchase totals =	$894.29		$961.7068	$961.70	$961.70	$961.60