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	$129.67	12.247%	$145.5507	$145.55	$145.55	$145.60
Purchase #2	$106.78	11.717%	$119.2914	$119.29	$119.30	$119.30
Purchase #3	$153.90	10.498%	$170.0564	$170.06	$170.05	$170.10
Purchase #4	$225.47	9.208%	$246.2313	$246.23	$246.25	$246.20
Purchase #5	$204.63	7.256%	$219.478	$219.48	$219.50	$219.50
Purchase #6	$34.80	7.495%	$37.4083	$37.41	$37.40	$37.40
Purchase #7	$109.30	13.188%	$123.7145	$123.71	$123.70	$123.70
7 purchase totals =	$964.55		$1,061.7306	$1,061.73	$1,061.75	$1,061.80