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	$225.93	12.171%	$253.4279	$253.43	$253.45	$253.40
Purchase #2	$89.83	4.651%	$94.008	$94.01	$94.00	$94.00
Purchase #3	$171.77	4.709%	$179.8586	$179.86	$179.85	$179.90
Purchase #4	$19.77	12.252%	$22.1922	$22.19	$22.20	$22.20
Purchase #5	$199.34	11.217%	$221.7	$221.70	$221.70	$221.70
Purchase #6	$219.97	6.320%	$233.8721	$233.87	$233.85	$233.90
Purchase #7	$47.98	11.309%	$53.4061	$53.41	$53.40	$53.40
7 purchase totals =	$974.59		$1,058.4649	$1,058.47	$1,058.45	$1,058.50