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	$50.48	7.451%	$54.2413	$54.24	$54.25	$54.20
Purchase #2	$53.55	8.817%	$58.2715	$58.27	$58.25	$58.30
Purchase #3	$205.25	9.102%	$223.9319	$223.93	$223.95	$223.90
Purchase #4	$84.62	11.570%	$94.4105	$94.41	$94.40	$94.40
Purchase #5	$79.33	8.233%	$85.8612	$85.86	$85.85	$85.90
Purchase #6	$144.51	13.514%	$164.0391	$164.04	$164.05	$164.00
Purchase #7	$180.38	6.264%	$191.679	$191.68	$191.70	$191.70
7 purchase totals =	$798.12		$872.4345	$872.43	$872.45	$872.40