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	$84.47	13.224%	$95.6403	$95.64	$95.65	$95.60
Purchase #2	$188.51	10.422%	$208.1565	$208.16	$208.15	$208.20
Purchase #3	$236.65	9.355%	$258.7886	$258.79	$258.80	$258.80
Purchase #4	$29.85	13.410%	$33.8529	$33.85	$33.85	$33.90
Purchase #5	$127.73	11.431%	$142.3308	$142.33	$142.35	$142.30
Purchase #6	$186.65	7.442%	$200.5405	$200.54	$200.55	$200.50
Purchase #7	$118.35	10.179%	$130.3968	$130.40	$130.40	$130.40
7 purchase totals =	$972.21		$1,069.7064	$1,069.71	$1,069.75	$1,069.70