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	$176.40	11.649%	$196.9488	$196.95	$196.95	$196.90
Purchase #2	$223.59	9.873%	$245.665	$245.67	$245.65	$245.70
Purchase #3	$132.95	3.371%	$137.4317	$137.43	$137.45	$137.40
Purchase #4	$209.29	9.791%	$229.7816	$229.78	$229.80	$229.80
Purchase #5	$223.98	10.400%	$247.2739	$247.27	$247.25	$247.30
Purchase #6	$30.93	8.820%	$33.658	$33.66	$33.65	$33.70
Purchase #7	$210.37	13.161%	$238.0568	$238.06	$238.05	$238.10
7 purchase totals =	$1,207.51		$1,328.8158	$1,328.82	$1,328.80	$1,328.90