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	$59.42	8.654%	$64.5622	$64.56	$64.55	$64.60
Purchase #2	$153.55	13.112%	$173.6835	$173.68	$173.70	$173.70
Purchase #3	$75.68	8.712%	$82.2732	$82.27	$82.25	$82.30
Purchase #4	$20.35	5.743%	$21.5187	$21.52	$21.50	$21.50
Purchase #5	$41.43	4.352%	$43.233	$43.23	$43.25	$43.20
Purchase #6	$170.31	6.306%	$181.0497	$181.05	$181.05	$181.00
Purchase #7	$182.98	8.776%	$199.0383	$199.04	$199.05	$199.00
7 purchase totals =	$703.72		$765.3586	$765.35	$765.35	$765.30