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	$50.73	11.476%	$56.5518	$56.55	$56.55	$56.60
Purchase #2	$29.77	13.330%	$33.7383	$33.74	$33.75	$33.70
Purchase #3	$178.71	6.480%	$190.2904	$190.29	$190.30	$190.30
Purchase #4	$156.96	11.682%	$175.2961	$175.30	$175.30	$175.30
Purchase #5	$158.95	8.271%	$172.0968	$172.10	$172.10	$172.10
Purchase #6	$165.32	8.650%	$179.6202	$179.62	$179.60	$179.60
Purchase #7	$124.85	9.849%	$137.1465	$137.15	$137.15	$137.10
7 purchase totals =	$865.29		$944.7401	$944.75	$944.75	$944.70