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	$82.40	8.723%	$89.5878	$89.59	$89.60	$89.60
Purchase #2	$92.43	4.147%	$96.2631	$96.26	$96.25	$96.30
Purchase #3	$137.50	6.774%	$146.8143	$146.81	$146.80	$146.80
Purchase #4	$139.57	7.841%	$150.5137	$150.51	$150.50	$150.50
Purchase #5	$169.86	7.760%	$183.0411	$183.04	$183.05	$183.00
Purchase #6	$92.56	4.581%	$96.8002	$96.80	$96.80	$96.80
Purchase #7	$241.77	13.689%	$274.8659	$274.87	$274.85	$274.90
7 purchase totals =	$956.09		$1,037.8861	$1,037.88	$1,037.85	$1,037.90