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	$30.32	7.368%	$32.554	$32.55	$32.55	$32.60
Purchase #2	$17.91	12.511%	$20.1507	$20.15	$20.15	$20.20
Purchase #3	$165.90	7.756%	$178.7672	$178.77	$178.75	$178.80
Purchase #4	$95.45	8.408%	$103.4754	$103.48	$103.50	$103.50
Purchase #5	$21.38	5.113%	$22.4732	$22.47	$22.45	$22.50
Purchase #6	$122.54	6.468%	$130.4659	$130.47	$130.45	$130.50
Purchase #7	$69.72	4.498%	$72.856	$72.86	$72.85	$72.90
7 purchase totals =	$523.22		$560.7424	$560.75	$560.70	$561.00