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	$143.48	4.668%	$150.1776	$150.18	$150.20	$150.20
Purchase #2	$11.78	8.118%	$12.7363	$12.74	$12.75	$12.70
Purchase #3	$71.27	3.131%	$73.5015	$73.50	$73.50	$73.50
Purchase #4	$211.45	5.225%	$222.4983	$222.50	$222.50	$222.50
Purchase #5	$183.83	4.185%	$191.5233	$191.52	$191.50	$191.50
Purchase #6	$109.78	5.692%	$116.0287	$116.03	$116.05	$116.00
Purchase #7	$220.71	5.583%	$233.0322	$233.03	$233.05	$233.00
7 purchase totals =	$952.30		$999.4979	$999.50	$999.55	$999.40