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	$229.92	6.758%	$245.458	$245.46	$245.45	$245.50
Purchase #2	$120.54	10.634%	$133.3582	$133.36	$133.35	$133.40
Purchase #3	$146.81	6.613%	$156.5185	$156.52	$156.50	$156.50
Purchase #4	$161.52	9.676%	$177.1487	$177.15	$177.15	$177.10
Purchase #5	$165.50	13.684%	$188.147	$188.15	$188.15	$188.10
Purchase #6	$62.63	8.397%	$67.889	$67.89	$67.90	$67.90
Purchase #7	$176.25	13.445%	$199.9468	$199.95	$199.95	$199.90
7 purchase totals =	$1,063.17		$1,168.4662	$1,168.48	$1,168.45	$1,168.40