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	$138.61	8.769%	$150.7647	$150.76	$150.75	$150.80
Purchase #2	$134.47	13.422%	$152.5186	$152.52	$152.50	$152.50
Purchase #3	$114.75	12.184%	$128.7311	$128.73	$128.75	$128.70
Purchase #4	$19.82	5.214%	$20.8534	$20.85	$20.85	$20.90
Purchase #5	$146.95	13.674%	$167.0439	$167.04	$167.05	$167.00
Purchase #6	$119.56	9.751%	$131.2183	$131.22	$131.20	$131.20
Purchase #7	$235.35	10.792%	$260.749	$260.75	$260.75	$260.70
7 purchase totals =	$909.51		$1,011.8790	$1,011.87	$1,011.85	$1,011.80