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	$244.31	5.125%	$256.8309	$256.83	$256.85	$256.80
Purchase #2	$12.44	5.452%	$13.1182	$13.12	$13.10	$13.10
Purchase #3	$237.48	11.795%	$265.4908	$265.49	$265.50	$265.50
Purchase #4	$56.67	10.419%	$62.5744	$62.57	$62.55	$62.60
Purchase #5	$189.50	10.452%	$209.3065	$209.31	$209.30	$209.30
Purchase #6	$48.41	13.316%	$54.8563	$54.86	$54.85	$54.90
Purchase #7	$211.34	3.711%	$219.1828	$219.18	$219.20	$219.20
7 purchase totals =	$1,000.15		$1,081.3599	$1,081.36	$1,081.35	$1,081.40