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	$146.40	7.275%	$157.0506	$157.05	$157.05	$157.10
Purchase #2	$30.29	7.215%	$32.4754	$32.48	$32.50	$32.50
Purchase #3	$62.56	13.496%	$71.0031	$71.00	$71.00	$71.00
Purchase #4	$189.98	5.756%	$200.9152	$200.92	$200.90	$200.90
Purchase #5	$169.34	7.380%	$181.8373	$181.84	$181.85	$181.80
Purchase #6	$82.73	10.708%	$91.5887	$91.59	$91.60	$91.60
Purchase #7	$219.75	12.106%	$246.3529	$246.35	$246.35	$246.40
7 purchase totals =	$901.05		$981.2232	$981.23	$981.25	$981.30