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	$223.43	7.701%	$240.6363	$240.64	$240.65	$240.60
Purchase #2	$24.91	13.523%	$28.2786	$28.28	$28.30	$28.30
Purchase #3	$84.82	6.707%	$90.5089	$90.51	$90.50	$90.50
Purchase #4	$152.89	6.340%	$162.5832	$162.58	$162.60	$162.60
Purchase #5	$202.44	6.612%	$215.8253	$215.83	$215.85	$215.80
Purchase #6	$143.38	6.517%	$152.7241	$152.72	$152.70	$152.70
Purchase #7	$225.59	3.277%	$232.9826	$232.98	$233.00	$233.00
7 purchase totals =	$1,057.46		$1,123.5390	$1,123.54	$1,123.60	$1,123.50