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	$85.87	12.841%	$96.8966	$96.90	$96.90	$96.90
Purchase #2	$95.51	10.112%	$105.168	$105.17	$105.15	$105.20
Purchase #3	$138.42	4.631%	$144.8302	$144.83	$144.85	$144.80
Purchase #4	$199.52	12.780%	$225.0187	$225.02	$225.00	$225.00
Purchase #5	$234.91	6.554%	$250.306	$250.31	$250.30	$250.30
Purchase #6	$83.75	7.323%	$89.883	$89.88	$89.90	$89.90
Purchase #7	$195.65	6.397%	$208.1657	$208.17	$208.15	$208.20
7 purchase totals =	$1,033.63		$1,120.2682	$1,120.28	$1,120.25	$1,120.30