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	$40.78	10.301%	$44.9807	$44.98	$45.00	$45.00
Purchase #2	$104.97	4.524%	$109.7188	$109.72	$109.70	$109.70
Purchase #3	$10.32	12.583%	$11.6186	$11.62	$11.60	$11.60
Purchase #4	$57.54	3.459%	$59.5303	$59.53	$59.55	$59.50
Purchase #5	$223.44	10.867%	$247.7212	$247.72	$247.70	$247.70
Purchase #6	$35.85	10.869%	$39.7465	$39.75	$39.75	$39.70
Purchase #7	$185.49	7.196%	$198.8379	$198.84	$198.85	$198.80
7 purchase totals =	$658.39		$712.1540	$712.16	$712.15	$712.00