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	$73.30	12.645%	$82.5688	$82.57	$82.55	$82.60
Purchase #2	$200.28	13.454%	$227.2257	$227.23	$227.25	$227.20
Purchase #3	$160.50	13.733%	$182.5415	$182.54	$182.55	$182.50
Purchase #4	$32.72	6.588%	$34.8756	$34.88	$34.90	$34.90
Purchase #5	$167.43	10.129%	$184.389	$184.39	$184.40	$184.40
Purchase #6	$132.62	3.391%	$137.1171	$137.12	$137.10	$137.10
Purchase #7	$32.73	3.145%	$33.7594	$33.76	$33.75	$33.80
7 purchase totals =	$799.58		$882.4771	$882.49	$882.50	$882.50