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	$65.68	8.680%	$71.381	$71.38	$71.40	$71.40
Purchase #2	$21.25	12.340%	$23.8723	$23.87	$23.85	$23.90
Purchase #3	$86.83	4.539%	$90.7712	$90.77	$90.75	$90.80
Purchase #4	$75.81	5.168%	$79.7279	$79.73	$79.75	$79.70
Purchase #5	$54.27	7.446%	$58.3109	$58.31	$58.30	$58.30
Purchase #6	$177.49	10.563%	$196.2383	$196.24	$196.25	$196.20
Purchase #7	$92.65	6.556%	$98.7241	$98.72	$98.70	$98.70
7 purchase totals =	$573.98		$619.0257	$619.02	$619.00	$619.00