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	$132.89	9.757%	$145.8561	$145.86	$145.85	$145.90
Purchase #2	$9.61	10.818%	$10.6496	$10.65	$10.65	$10.60
Purchase #3	$194.37	11.538%	$216.7964	$216.80	$216.80	$216.80
Purchase #4	$171.66	4.721%	$179.7641	$179.76	$179.75	$179.80
Purchase #5	$61.53	6.694%	$65.6488	$65.65	$65.65	$65.60
Purchase #6	$117.61	11.606%	$131.2598	$131.26	$131.25	$131.30
Purchase #7	$172.63	3.278%	$178.2888	$178.29	$178.30	$178.30
7 purchase totals =	$860.30		$928.2636	$928.27	$928.25	$928.30