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	$188.96	10.525%	$208.848	$208.85	$208.85	$208.80
Purchase #2	$75.74	8.316%	$82.0385	$82.04	$82.05	$82.00
Purchase #3	$174.82	12.611%	$196.8666	$196.87	$196.85	$196.90
Purchase #4	$59.46	5.388%	$62.6637	$62.66	$62.65	$62.70
Purchase #5	$134.60	5.774%	$142.3718	$142.37	$142.35	$142.40
Purchase #6	$247.91	11.552%	$276.5486	$276.55	$276.55	$276.50
Purchase #7	$97.43	3.837%	$101.1684	$101.17	$101.15	$101.20
7 purchase totals =	$978.92		$1,070.5056	$1,070.51	$1,070.45	$1,070.50