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	$219.43	4.517%	$229.3417	$229.34	$229.35	$229.30
Purchase #2	$152.89	8.173%	$165.3857	$165.39	$165.40	$165.40
Purchase #3	$16.67	9.332%	$18.2256	$18.23	$18.25	$18.20
Purchase #4	$49.86	11.133%	$55.4109	$55.41	$55.40	$55.40
Purchase #5	$194.54	5.337%	$204.9226	$204.92	$204.90	$204.90
Purchase #6	$31.62	12.446%	$35.5554	$35.56	$35.55	$35.60
Purchase #7	$48.47	13.477%	$55.0023	$55.00	$55.00	$55.00
7 purchase totals =	$713.48		$763.8442	$763.85	$763.85	$763.80