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	$117.29	11.540%	$130.8253	$130.83	$130.85	$130.80
Purchase #2	$205.26	8.815%	$223.3537	$223.35	$223.35	$223.40
Purchase #3	$245.70	13.751%	$279.4862	$279.49	$279.50	$279.50
Purchase #4	$39.69	11.725%	$44.3437	$44.34	$44.35	$44.30
Purchase #5	$53.25	10.867%	$59.0367	$59.04	$59.05	$59.00
Purchase #6	$18.70	8.724%	$20.3314	$20.33	$20.35	$20.30
Purchase #7	$239.50	10.594%	$264.8726	$264.87	$264.85	$264.90
7 purchase totals =	$919.39		$1,022.2496	$1,022.25	$1,022.30	$1,022.20