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	$62.45	6.799%	$66.696	$66.70	$66.70	$66.70
Purchase #2	$79.58	12.437%	$89.4774	$89.48	$89.50	$89.50
Purchase #3	$57.90	7.722%	$62.371	$62.37	$62.35	$62.40
Purchase #4	$55.95	8.736%	$60.8378	$60.84	$60.85	$60.80
Purchase #5	$64.33	5.195%	$67.6719	$67.67	$67.65	$67.70
Purchase #6	$31.55	12.412%	$35.466	$35.47	$35.45	$35.50
Purchase #7	$138.45	10.342%	$152.7685	$152.77	$152.75	$152.80
7 purchase totals =	$490.21		$535.2886	$535.30	$535.25	$535.40