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	$214.53	4.714%	$224.6429	$224.64	$224.65	$224.60
Purchase #2	$92.68	13.424%	$105.1214	$105.12	$105.10	$105.10
Purchase #3	$32.34	11.147%	$35.9449	$35.94	$35.95	$35.90
Purchase #4	$52.70	12.790%	$59.4403	$59.44	$59.45	$59.40
Purchase #5	$9.38	7.109%	$10.0468	$10.05	$10.05	$10.00
Purchase #6	$191.37	12.344%	$214.9927	$214.99	$215.00	$215.00
Purchase #7	$65.46	10.779%	$72.5159	$72.52	$72.50	$72.50
7 purchase totals =	$658.46		$722.7049	$722.70	$722.70	$722.50