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	$112.63	12.142%	$126.3055	$126.31	$126.30	$126.30
Purchase #2	$20.45	4.159%	$21.3005	$21.30	$21.30	$21.30
Purchase #3	$93.96	7.846%	$101.3321	$101.33	$101.35	$101.30
Purchase #4	$161.63	11.314%	$179.9168	$179.92	$179.90	$179.90
Purchase #5	$5.46	8.435%	$5.9206	$5.92	$5.90	$5.90
Purchase #6	$40.47	12.562%	$45.5538	$45.55	$45.55	$45.60
Purchase #7	$211.93	11.123%	$235.503	$235.50	$235.50	$235.50
7 purchase totals =	$646.53		$715.8323	$715.83	$715.80	$715.80