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	$204.56	9.747%	$224.4985	$224.50	$224.50	$224.50
Purchase #2	$46.71	8.529%	$50.6939	$50.69	$50.70	$50.70
Purchase #3	$80.54	12.818%	$90.8636	$90.86	$90.85	$90.90
Purchase #4	$92.88	13.221%	$105.1597	$105.16	$105.15	$105.20
Purchase #5	$209.33	7.228%	$224.4604	$224.46	$224.45	$224.50
Purchase #6	$165.88	7.838%	$178.8817	$178.88	$178.90	$178.90
Purchase #7	$177.31	10.335%	$195.635	$195.64	$195.65	$195.60
7 purchase totals =	$977.21		$1,070.1928	$1,070.19	$1,070.20	$1,070.30