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	$131.95	11.637%	$147.305	$147.31	$147.30	$147.30
Purchase #2	$27.64	12.613%	$31.1262	$31.13	$31.15	$31.10
Purchase #3	$68.30	5.409%	$71.9943	$71.99	$72.00	$72.00
Purchase #4	$78.94	13.114%	$89.2922	$89.29	$89.30	$89.30
Purchase #5	$66.28	4.813%	$69.4701	$69.47	$69.45	$69.50
Purchase #6	$112.54	11.404%	$125.3741	$125.37	$125.35	$125.40
Purchase #7	$89.87	3.504%	$93.019	$93.02	$93.00	$93.00
7 purchase totals =	$575.52		$627.5809	$627.58	$627.55	$627.60