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	$185.45	12.494%	$208.6201	$208.62	$208.60	$208.60
Purchase #2	$111.71	12.573%	$125.7553	$125.76	$125.75	$125.80
Purchase #3	$36.62	3.516%	$37.9076	$37.91	$37.90	$37.90
Purchase #4	$53.74	10.650%	$59.4633	$59.46	$59.45	$59.50
Purchase #5	$157.83	11.138%	$175.4091	$175.41	$175.40	$175.40
Purchase #6	$209.49	3.734%	$217.3124	$217.31	$217.30	$217.30
Purchase #7	$55.81	12.760%	$62.9314	$62.93	$62.95	$62.90
7 purchase totals =	$810.65		$887.3992	$887.40	$887.35	$887.40