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	$41.28	4.527%	$43.1487	$43.15	$43.15	$43.10
Purchase #2	$127.93	10.385%	$141.2155	$141.22	$141.20	$141.20
Purchase #3	$52.68	3.147%	$54.3378	$54.34	$54.35	$54.30
Purchase #4	$205.85	7.496%	$221.2805	$221.28	$221.30	$221.30
Purchase #5	$188.88	11.837%	$211.2377	$211.24	$211.25	$211.20
Purchase #6	$115.33	12.630%	$129.8962	$129.90	$129.90	$129.90
Purchase #7	$54.66	11.161%	$60.7606	$60.76	$60.75	$60.80
7 purchase totals =	$786.61		$861.8770	$861.89	$861.90	$861.80