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	$62.38	5.526%	$65.8271	$65.83	$65.85	$65.80
Purchase #2	$197.94	12.399%	$222.4826	$222.48	$222.50	$222.50
Purchase #3	$25.89	4.735%	$27.1159	$27.12	$27.10	$27.10
Purchase #4	$110.60	7.742%	$119.1627	$119.16	$119.15	$119.20
Purchase #5	$67.30	5.217%	$70.811	$70.81	$70.80	$70.80
Purchase #6	$45.38	10.785%	$50.2742	$50.27	$50.25	$50.30
Purchase #7	$168.60	9.754%	$185.0452	$185.05	$185.05	$185.00
7 purchase totals =	$678.09		$740.7187	$740.72	$740.70	$740.70