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	$94.31	8.128%	$101.9755	$101.98	$102.00	$102.00
Purchase #2	$21.36	13.193%	$24.178	$24.18	$24.20	$24.20
Purchase #3	$165.44	12.345%	$185.8636	$185.86	$185.85	$185.90
Purchase #4	$38.66	9.742%	$42.4263	$42.43	$42.45	$42.40
Purchase #5	$96.48	10.223%	$106.3432	$106.34	$106.35	$106.30
Purchase #6	$77.88	11.639%	$86.9445	$86.94	$86.95	$86.90
Purchase #7	$137.44	10.632%	$152.0526	$152.05	$152.05	$152.10
7 purchase totals =	$631.57		$699.7837	$699.78	$699.85	$699.80