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	$42.31	8.107%	$45.7401	$45.74	$45.75	$45.70
Purchase #2	$193.42	11.649%	$215.9515	$215.95	$215.95	$216.00
Purchase #3	$34.44	7.525%	$37.0316	$37.03	$37.05	$37.00
Purchase #4	$102.67	8.839%	$111.745	$111.75	$111.75	$111.70
Purchase #5	$236.70	11.796%	$264.6211	$264.62	$264.60	$264.60
Purchase #6	$10.43	7.614%	$11.2241	$11.22	$11.20	$11.20
Purchase #7	$77.54	10.326%	$85.5468	$85.55	$85.55	$85.50
7 purchase totals =	$697.51		$771.8602	$771.86	$771.85	$771.70