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	$247.55	6.637%	$263.9799	$263.98	$264.00	$264.00
Purchase #2	$161.45	5.852%	$170.8981	$170.90	$170.90	$170.90
Purchase #3	$214.28	13.155%	$242.4685	$242.47	$242.45	$242.50
Purchase #4	$130.70	4.528%	$136.6181	$136.62	$136.60	$136.60
Purchase #5	$46.37	6.194%	$49.2422	$49.24	$49.25	$49.20
Purchase #6	$36.73	11.321%	$40.8882	$40.89	$40.90	$40.90
Purchase #7	$37.45	10.779%	$41.4867	$41.49	$41.50	$41.50
7 purchase totals =	$874.53		$945.5817	$945.59	$945.60	$945.60