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	$54.69	8.860%	$59.5355	$59.54	$59.55	$59.50
Purchase #2	$69.83	3.782%	$72.471	$72.47	$72.45	$72.50
Purchase #3	$165.73	8.471%	$179.769	$179.77	$179.75	$179.80
Purchase #4	$160.48	9.768%	$176.1557	$176.16	$176.15	$176.20
Purchase #5	$140.85	8.586%	$152.9434	$152.94	$152.95	$152.90
Purchase #6	$89.35	5.627%	$94.3777	$94.38	$94.40	$94.40
Purchase #7	$185.87	13.359%	$210.7004	$210.70	$210.70	$210.70
7 purchase totals =	$866.80		$945.9527	$945.96	$945.95	$946.00