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	$117.42	11.781%	$131.2533	$131.25	$131.25	$131.30
Purchase #2	$177.89	3.235%	$183.6447	$183.64	$183.65	$183.60
Purchase #3	$55.48	10.682%	$61.4064	$61.41	$61.40	$61.40
Purchase #4	$59.76	7.112%	$64.0101	$64.01	$64.00	$64.00
Purchase #5	$235.29	8.547%	$255.4002	$255.40	$255.40	$255.40
Purchase #6	$59.49	10.150%	$65.5282	$65.53	$65.55	$65.50
Purchase #7	$166.82	13.580%	$189.4742	$189.47	$189.45	$189.50
7 purchase totals =	$872.15		$950.7171	$950.71	$950.70	$950.70