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	$11.62	5.562%	$12.2663	$12.27	$12.25	$12.30
Purchase #2	$56.43	13.577%	$64.0915	$64.09	$64.10	$64.10
Purchase #3	$216.80	8.114%	$234.3912	$234.39	$234.40	$234.40
Purchase #4	$25.90	10.762%	$28.6874	$28.69	$28.70	$28.70
Purchase #5	$27.56	13.252%	$31.2123	$31.21	$31.20	$31.20
Purchase #6	$81.76	4.499%	$85.4384	$85.44	$85.45	$85.40
Purchase #7	$30.45	5.864%	$32.2356	$32.24	$32.25	$32.20
7 purchase totals =	$450.52		$488.3227	$488.33	$488.35	$488.30