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	$225.54	7.681%	$242.8637	$242.86	$242.85	$242.90
Purchase #2	$21.54	13.518%	$24.4518	$24.45	$24.45	$24.50
Purchase #3	$198.90	6.407%	$211.6435	$211.64	$211.65	$211.60
Purchase #4	$99.56	5.284%	$104.8208	$104.82	$104.80	$104.80
Purchase #5	$137.79	13.213%	$155.9962	$156.00	$156.00	$156.00
Purchase #6	$90.84	4.620%	$95.0368	$95.04	$95.05	$95.00
Purchase #7	$202.32	10.254%	$223.0659	$223.07	$223.05	$223.10
7 purchase totals =	$976.49		$1,057.8787	$1,057.88	$1,057.85	$1,057.90