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	$131.58	7.638%	$141.6301	$141.63	$141.65	$141.60
Purchase #2	$146.28	3.510%	$151.4144	$151.41	$151.40	$151.40
Purchase #3	$104.69	5.773%	$110.7338	$110.73	$110.75	$110.70
Purchase #4	$79.72	3.715%	$82.6816	$82.68	$82.70	$82.70
Purchase #5	$93.71	4.250%	$97.6927	$97.69	$97.70	$97.70
Purchase #6	$88.72	6.258%	$94.2721	$94.27	$94.25	$94.30
Purchase #7	$69.94	10.743%	$77.4537	$77.45	$77.45	$77.50
7 purchase totals =	$714.64		$755.8784	$755.86	$755.90	$755.90