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	$58.40	11.138%	$64.9046	$64.90	$64.90	$64.90
Purchase #2	$65.73	9.874%	$72.2202	$72.22	$72.20	$72.20
Purchase #3	$223.94	13.863%	$254.9848	$254.98	$255.00	$255.00
Purchase #4	$129.47	7.865%	$139.6528	$139.65	$139.65	$139.70
Purchase #5	$179.89	4.704%	$188.352	$188.35	$188.35	$188.40
Purchase #6	$219.96	10.816%	$243.7509	$243.75	$243.75	$243.80
Purchase #7	$86.67	12.199%	$97.2429	$97.24	$97.25	$97.20
7 purchase totals =	$964.06		$1,061.1082	$1,061.09	$1,061.10	$1,061.20