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	$219.46	4.505%	$229.3467	$229.35	$229.35	$229.30
Purchase #2	$86.77	4.847%	$90.9757	$90.98	$91.00	$91.00
Purchase #3	$104.64	11.145%	$116.3021	$116.30	$116.30	$116.30
Purchase #4	$11.94	7.761%	$12.8667	$12.87	$12.85	$12.90
Purchase #5	$159.54	5.548%	$168.3913	$168.39	$168.40	$168.40
Purchase #6	$206.80	13.568%	$234.8586	$234.86	$234.85	$234.90
Purchase #7	$82.49	12.842%	$93.0834	$93.08	$93.10	$93.10
7 purchase totals =	$871.64		$945.8245	$945.83	$945.85	$945.90