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	$132.31	10.445%	$146.1298	$146.13	$146.15	$146.10
Purchase #2	$62.81	12.594%	$70.7203	$70.72	$70.70	$70.70
Purchase #3	$179.61	5.279%	$189.0916	$189.09	$189.10	$189.10
Purchase #4	$209.93	6.442%	$223.4537	$223.45	$223.45	$223.50
Purchase #5	$134.89	8.668%	$146.5823	$146.58	$146.60	$146.60
Purchase #6	$127.37	3.567%	$131.9133	$131.91	$131.90	$131.90
Purchase #7	$49.76	11.704%	$55.5839	$55.58	$55.60	$55.60
7 purchase totals =	$896.68		$963.4749	$963.46	$963.50	$963.50