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	$44.50	6.401%	$47.3484	$47.35	$47.35	$47.30
Purchase #2	$43.47	4.514%	$45.4322	$45.43	$45.45	$45.40
Purchase #3	$247.43	3.819%	$256.8794	$256.88	$256.90	$256.90
Purchase #4	$83.84	8.834%	$91.2464	$91.25	$91.25	$91.20
Purchase #5	$67.93	13.111%	$76.8363	$76.84	$76.85	$76.80
Purchase #6	$96.53	8.493%	$104.7283	$104.73	$104.75	$104.70
Purchase #7	$219.25	5.513%	$231.3373	$231.34	$231.35	$231.30
7 purchase totals =	$802.95		$853.8083	$853.82	$853.90	$853.60