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	$143.57	6.108%	$152.3393	$152.34	$152.35	$152.30
Purchase #2	$194.93	10.859%	$216.0974	$216.10	$216.10	$216.10
Purchase #3	$241.33	13.571%	$274.0809	$274.08	$274.10	$274.10
Purchase #4	$20.42	12.343%	$22.9404	$22.94	$22.95	$22.90
Purchase #5	$77.52	6.867%	$82.8433	$82.84	$82.85	$82.80
Purchase #6	$76.58	4.555%	$80.0682	$80.07	$80.05	$80.10
Purchase #7	$89.60	11.513%	$99.9156	$99.92	$99.90	$99.90
7 purchase totals =	$843.95		$928.2851	$928.29	$928.30	$928.20