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	$224.81	8.160%	$243.1545	$243.15	$243.15	$243.20
Purchase #2	$111.81	11.306%	$124.4512	$124.45	$124.45	$124.50
Purchase #3	$192.30	4.459%	$200.8747	$200.87	$200.85	$200.90
Purchase #4	$215.78	3.209%	$222.7044	$222.70	$222.70	$222.70
Purchase #5	$47.75	4.773%	$50.0291	$50.03	$50.05	$50.00
Purchase #6	$72.76	11.176%	$80.8917	$80.89	$80.90	$80.90
Purchase #7	$60.55	8.645%	$65.7845	$65.78	$65.80	$65.80
7 purchase totals =	$925.76		$987.8901	$987.87	$987.90	$988.00