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	$46.51	13.489%	$52.7837	$52.78	$52.80	$52.80
Purchase #2	$238.82	11.323%	$265.8616	$265.86	$265.85	$265.90
Purchase #3	$165.27	7.773%	$178.1164	$178.12	$178.10	$178.10
Purchase #4	$174.48	8.848%	$189.918	$189.92	$189.90	$189.90
Purchase #5	$96.58	11.110%	$107.31	$107.31	$107.30	$107.30
Purchase #6	$48.51	8.773%	$52.7658	$52.77	$52.75	$52.80
Purchase #7	$37.38	8.427%	$40.53	$40.53	$40.55	$40.50
7 purchase totals =	$807.55		$887.2855	$887.29	$887.25	$887.30