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	$233.52	13.280%	$264.5315	$264.53	$264.55	$264.50
Purchase #2	$31.62	7.219%	$33.9026	$33.90	$33.90	$33.90
Purchase #3	$144.38	10.662%	$159.7738	$159.77	$159.75	$159.80
Purchase #4	$72.88	3.600%	$75.5037	$75.50	$75.50	$75.50
Purchase #5	$222.74	13.407%	$252.6028	$252.60	$252.60	$252.60
Purchase #6	$168.86	9.779%	$185.3728	$185.37	$185.35	$185.40
Purchase #7	$55.71	7.782%	$60.0454	$60.05	$60.05	$60.00
7 purchase totals =	$929.71		$1,031.7326	$1,031.72	$1,031.70	$1,031.70