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	$214.41	12.669%	$241.5736	$241.57	$241.55	$241.60
Purchase #2	$113.95	5.780%	$120.5363	$120.54	$120.55	$120.50
Purchase #3	$161.96	4.563%	$169.3502	$169.35	$169.35	$169.40
Purchase #4	$24.74	12.715%	$27.8857	$27.89	$27.90	$27.90
Purchase #5	$141.28	8.124%	$152.7576	$152.76	$152.75	$152.80
Purchase #6	$57.52	13.244%	$65.1379	$65.14	$65.15	$65.10
Purchase #7	$28.78	11.443%	$32.0733	$32.07	$32.05	$32.10
7 purchase totals =	$742.64		$809.3146	$809.32	$809.30	$809.40