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	$231.66	4.495%	$242.0731	$242.07	$242.05	$242.10
Purchase #2	$75.72	12.788%	$85.4031	$85.40	$85.40	$85.40
Purchase #3	$137.64	13.361%	$156.0301	$156.03	$156.05	$156.00
Purchase #4	$179.92	10.527%	$198.8602	$198.86	$198.85	$198.90
Purchase #5	$53.66	9.849%	$58.945	$58.95	$58.95	$58.90
Purchase #6	$210.98	10.489%	$233.1097	$233.11	$233.10	$233.10
Purchase #7	$119.40	3.540%	$123.6268	$123.63	$123.65	$123.60
7 purchase totals =	$1,008.98		$1,098.0480	$1,098.05	$1,098.05	$1,098.00