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	$100.48	10.515%	$111.0455	$111.05	$111.05	$111.00
Purchase #2	$83.97	9.200%	$91.6952	$91.70	$91.70	$91.70
Purchase #3	$123.72	5.485%	$130.506	$130.51	$130.50	$130.50
Purchase #4	$69.72	4.239%	$72.6754	$72.68	$72.70	$72.70
Purchase #5	$27.32	12.723%	$30.7959	$30.80	$30.80	$30.80
Purchase #6	$195.46	8.292%	$211.6675	$211.67	$211.65	$211.70
Purchase #7	$90.35	11.168%	$100.4403	$100.44	$100.45	$100.40
7 purchase totals =	$691.02		$748.8258	$748.85	$748.85	$748.80