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	$152.32	8.148%	$164.731	$164.73	$164.75	$164.70
Purchase #2	$29.77	3.399%	$30.7819	$30.78	$30.80	$30.80
Purchase #3	$39.96	8.206%	$43.2391	$43.24	$43.25	$43.20
Purchase #4	$84.27	6.374%	$89.6414	$89.64	$89.65	$89.60
Purchase #5	$105.31	6.501%	$112.1562	$112.16	$112.15	$112.20
Purchase #6	$62.52	10.483%	$69.074	$69.07	$69.05	$69.10
Purchase #7	$97.89	10.823%	$108.4846	$108.48	$108.50	$108.50
7 purchase totals =	$572.04		$618.1082	$618.10	$618.15	$618.10