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	$82.97	7.844%	$89.4782	$89.48	$89.50	$89.50
Purchase #2	$206.53	10.384%	$227.9761	$227.98	$228.00	$228.00
Purchase #3	$6.39	8.852%	$6.9556	$6.96	$6.95	$7.00
Purchase #4	$39.88	4.822%	$41.803	$41.80	$41.80	$41.80
Purchase #5	$216.98	4.108%	$225.8935	$225.89	$225.90	$225.90
Purchase #6	$221.89	10.323%	$244.7957	$244.80	$244.80	$244.80
Purchase #7	$40.77	11.118%	$45.3028	$45.30	$45.30	$45.30
7 purchase totals =	$815.41		$882.2049	$882.21	$882.25	$882.30