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	$200.83	6.348%	$213.5787	$213.58	$213.60	$213.60
Purchase #2	$90.91	9.354%	$99.4137	$99.41	$99.40	$99.40
Purchase #3	$177.43	7.637%	$190.9803	$190.98	$191.00	$191.00
Purchase #4	$74.44	10.737%	$82.4326	$82.43	$82.45	$82.40
Purchase #5	$211.91	9.177%	$231.357	$231.36	$231.35	$231.40
Purchase #6	$56.70	5.785%	$59.9801	$59.98	$60.00	$60.00
Purchase #7	$136.89	6.674%	$146.026	$146.03	$146.05	$146.00
7 purchase totals =	$949.11		$1,023.7684	$1,023.77	$1,023.85	$1,023.80