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	$153.34	10.771%	$169.8563	$169.86	$169.85	$169.90
Purchase #2	$36.70	7.194%	$39.3402	$39.34	$39.35	$39.30
Purchase #3	$223.30	11.440%	$248.8455	$248.85	$248.85	$248.80
Purchase #4	$80.89	11.285%	$90.0184	$90.02	$90.00	$90.00
Purchase #5	$142.40	10.343%	$157.1284	$157.13	$157.15	$157.10
Purchase #6	$183.43	11.829%	$205.1279	$205.13	$205.15	$205.10
Purchase #7	$108.42	10.378%	$119.6718	$119.67	$119.65	$119.70
7 purchase totals =	$928.48		$1,029.9885	$1,030.00	$1,030.00	$1,029.90