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	$188.56	10.821%	$208.9641	$208.96	$208.95	$209.00
Purchase #2	$99.81	5.380%	$105.1798	$105.18	$105.20	$105.20
Purchase #3	$184.97	3.121%	$190.7429	$190.74	$190.75	$190.70
Purchase #4	$29.69	6.759%	$31.6967	$31.70	$31.70	$31.70
Purchase #5	$134.60	12.453%	$151.3617	$151.36	$151.35	$151.40
Purchase #6	$175.35	12.318%	$196.9496	$196.95	$196.95	$196.90
Purchase #7	$145.55	8.287%	$157.6117	$157.61	$157.60	$157.60
7 purchase totals =	$958.53		$1,042.5065	$1,042.50	$1,042.50	$1,042.50