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	$164.78	10.742%	$182.4807	$182.48	$182.50	$182.50
Purchase #2	$94.55	6.330%	$100.535	$100.54	$100.55	$100.50
Purchase #3	$20.69	3.647%	$21.4446	$21.44	$21.45	$21.40
Purchase #4	$106.78	4.184%	$111.2477	$111.25	$111.25	$111.20
Purchase #5	$246.53	8.290%	$266.9673	$266.97	$266.95	$267.00
Purchase #6	$201.94	9.357%	$220.8355	$220.84	$220.85	$220.80
Purchase #7	$109.35	13.111%	$123.6869	$123.69	$123.70	$123.70
7 purchase totals =	$944.62		$1,027.1977	$1,027.21	$1,027.25	$1,027.10