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	$14.47	13.467%	$16.4187	$16.42	$16.40	$16.40
Purchase #2	$81.46	12.772%	$91.8641	$91.86	$91.85	$91.90
Purchase #3	$116.85	3.810%	$121.302	$121.30	$121.30	$121.30
Purchase #4	$187.79	4.545%	$196.3251	$196.33	$196.35	$196.30
Purchase #5	$64.43	12.801%	$72.6777	$72.68	$72.70	$72.70
Purchase #6	$45.52	3.849%	$47.2721	$47.27	$47.25	$47.30
Purchase #7	$161.42	11.230%	$179.5475	$179.55	$179.55	$179.50
7 purchase totals =	$671.94		$725.4072	$725.41	$725.40	$725.40