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	$45.69	5.842%	$48.3592	$48.36	$48.35	$48.40
Purchase #2	$92.83	7.377%	$99.6781	$99.68	$99.70	$99.70
Purchase #3	$202.78	11.344%	$225.7834	$225.78	$225.80	$225.80
Purchase #4	$37.71	11.493%	$42.044	$42.04	$42.05	$42.00
Purchase #5	$73.41	11.434%	$81.8037	$81.80	$81.80	$81.80
Purchase #6	$223.94	9.524%	$245.268	$245.27	$245.25	$245.30
Purchase #7	$169.83	8.665%	$184.5458	$184.55	$184.55	$184.50
7 purchase totals =	$846.19		$927.4822	$927.48	$927.50	$927.50