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	$76.94	10.722%	$85.1895	$85.19	$85.20	$85.20
Purchase #2	$135.48	12.419%	$152.3053	$152.31	$152.30	$152.30
Purchase #3	$9.54	8.315%	$10.3333	$10.33	$10.35	$10.30
Purchase #4	$101.96	11.696%	$113.8852	$113.89	$113.90	$113.90
Purchase #5	$154.72	6.400%	$164.6221	$164.62	$164.60	$164.60
Purchase #6	$102.45	12.226%	$114.9755	$114.98	$115.00	$115.00
Purchase #7	$76.26	8.620%	$82.8336	$82.83	$82.85	$82.80
7 purchase totals =	$657.35		$724.1445	$724.15	$724.20	$724.10