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	$234.47	12.774%	$264.4212	$264.42	$264.40	$264.40
Purchase #2	$137.57	10.728%	$152.3285	$152.33	$152.35	$152.30
Purchase #3	$47.84	8.236%	$51.7801	$51.78	$51.80	$51.80
Purchase #4	$59.72	12.802%	$67.3654	$67.37	$67.35	$67.40
Purchase #5	$154.74	9.700%	$169.7498	$169.75	$169.75	$169.70
Purchase #6	$221.67	7.594%	$238.5036	$238.50	$238.50	$238.50
Purchase #7	$150.45	10.761%	$166.6399	$166.64	$166.65	$166.60
7 purchase totals =	$1,006.46		$1,110.7885	$1,110.79	$1,110.80	$1,110.70