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	$114.69	3.168%	$118.3234	$118.32	$118.30	$118.30
Purchase #2	$37.75	7.499%	$40.5809	$40.58	$40.60	$40.60
Purchase #3	$114.37	13.818%	$130.1736	$130.17	$130.15	$130.20
Purchase #4	$66.81	10.524%	$73.8411	$73.84	$73.85	$73.80
Purchase #5	$95.78	9.570%	$104.9461	$104.95	$104.95	$104.90
Purchase #6	$20.54	5.183%	$21.6046	$21.60	$21.60	$21.60
Purchase #7	$165.52	11.809%	$185.0663	$185.07	$185.05	$185.10
7 purchase totals =	$615.46		$674.5360	$674.53	$674.50	$674.50