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	$233.39	12.760%	$263.1706	$263.17	$263.15	$263.20
Purchase #2	$151.75	13.473%	$172.1953	$172.20	$172.20	$172.20
Purchase #3	$199.63	8.277%	$216.1534	$216.15	$216.15	$216.20
Purchase #4	$226.42	6.839%	$241.9049	$241.90	$241.90	$241.90
Purchase #5	$86.43	3.320%	$89.2995	$89.30	$89.30	$89.30
Purchase #6	$38.86	5.389%	$40.9542	$40.95	$40.95	$41.00
Purchase #7	$85.70	6.534%	$91.2996	$91.30	$91.30	$91.30
7 purchase totals =	$1,022.18		$1,114.9775	$1,114.97	$1,114.95	$1,115.10