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	$96.73	12.108%	$108.4421	$108.44	$108.45	$108.40
Purchase #2	$95.53	5.269%	$100.5635	$100.56	$100.55	$100.60
Purchase #3	$245.88	3.320%	$254.0432	$254.04	$254.05	$254.00
Purchase #4	$121.89	7.445%	$130.9647	$130.96	$130.95	$131.00
Purchase #5	$234.40	5.758%	$247.8968	$247.90	$247.90	$247.90
Purchase #6	$9.41	11.558%	$10.4976	$10.50	$10.50	$10.50
Purchase #7	$151.67	7.368%	$162.845	$162.85	$162.85	$162.80
7 purchase totals =	$955.51		$1,015.2529	$1,015.25	$1,015.25	$1,015.20