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	$230.50	5.360%	$242.8548	$242.85	$242.85	$242.90
Purchase #2	$93.86	5.782%	$99.287	$99.29	$99.30	$99.30
Purchase #3	$59.37	12.863%	$67.0068	$67.01	$67.00	$67.00
Purchase #4	$146.70	12.367%	$164.8424	$164.84	$164.85	$164.80
Purchase #5	$198.98	7.123%	$213.1533	$213.15	$213.15	$213.20
Purchase #6	$33.58	11.251%	$37.3581	$37.36	$37.35	$37.40
Purchase #7	$40.82	13.863%	$46.4789	$46.48	$46.50	$46.50
7 purchase totals =	$803.81		$870.9813	$870.98	$871.00	$871.10