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	$223.99	8.421%	$242.8522	$242.85	$242.85	$242.90
Purchase #2	$170.63	11.612%	$190.4436	$190.44	$190.45	$190.40
Purchase #3	$214.52	8.641%	$233.0567	$233.06	$233.05	$233.10
Purchase #4	$25.31	4.377%	$26.4178	$26.42	$26.40	$26.40
Purchase #5	$236.35	8.196%	$255.7212	$255.72	$255.70	$255.70
Purchase #6	$54.88	8.350%	$59.4625	$59.46	$59.45	$59.50
Purchase #7	$90.97	6.266%	$96.6702	$96.67	$96.65	$96.70
7 purchase totals =	$1,016.65		$1,104.6242	$1,104.62	$1,104.55	$1,104.70