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	$208.47	6.338%	$221.6828	$221.68	$221.70	$221.70
Purchase #2	$35.95	4.728%	$37.6497	$37.65	$37.65	$37.60
Purchase #3	$213.57	12.482%	$240.2278	$240.23	$240.25	$240.20
Purchase #4	$78.59	9.405%	$85.9814	$85.98	$86.00	$86.00
Purchase #5	$226.62	12.399%	$254.7186	$254.72	$254.70	$254.70
Purchase #6	$9.87	10.545%	$10.9108	$10.91	$10.90	$10.90
Purchase #7	$99.81	5.521%	$105.3205	$105.32	$105.30	$105.30
7 purchase totals =	$872.88		$956.4916	$956.49	$956.50	$956.40