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	$141.75	6.638%	$151.1594	$151.16	$151.15	$151.20
Purchase #2	$13.63	6.556%	$14.5236	$14.52	$14.50	$14.50
Purchase #3	$80.69	8.277%	$87.3687	$87.37	$87.35	$87.40
Purchase #4	$79.95	11.370%	$89.0403	$89.04	$89.05	$89.00
Purchase #5	$20.58	6.135%	$21.8426	$21.84	$21.85	$21.80
Purchase #6	$85.94	6.366%	$91.4109	$91.41	$91.40	$91.40
Purchase #7	$43.77	5.276%	$46.0793	$46.08	$46.10	$46.10
7 purchase totals =	$466.31		$501.4248	$501.42	$501.40	$501.40