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	$177.65	7.689%	$191.3095	$191.31	$191.30	$191.30
Purchase #2	$190.84	10.691%	$211.2427	$211.24	$211.25	$211.20
Purchase #3	$126.54	11.420%	$140.9909	$140.99	$141.00	$141.00
Purchase #4	$128.80	10.780%	$142.6846	$142.68	$142.70	$142.70
Purchase #5	$133.38	8.833%	$145.1615	$145.16	$145.15	$145.20
Purchase #6	$245.77	3.160%	$253.5363	$253.54	$253.55	$253.50
Purchase #7	$88.87	13.482%	$100.8515	$100.85	$100.85	$100.90
7 purchase totals =	$1,091.85		$1,185.7770	$1,185.77	$1,185.80	$1,185.80