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	$171.56	10.374%	$189.3576	$189.36	$189.35	$189.40
Purchase #2	$59.81	4.262%	$62.3591	$62.36	$62.35	$62.40
Purchase #3	$191.53	4.216%	$199.6049	$199.60	$199.60	$199.60
Purchase #4	$90.51	10.263%	$99.799	$99.80	$99.80	$99.80
Purchase #5	$116.57	8.301%	$126.2465	$126.25	$126.25	$126.20
Purchase #6	$208.51	7.864%	$224.9072	$224.91	$224.90	$224.90
Purchase #7	$126.58	13.401%	$143.543	$143.54	$143.55	$143.50
7 purchase totals =	$965.07		$1,045.8173	$1,045.82	$1,045.80	$1,045.80