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	$128.72	6.321%	$136.8564	$136.86	$136.85	$136.90
Purchase #2	$139.42	6.444%	$148.4042	$148.40	$148.40	$148.40
Purchase #3	$40.28	4.352%	$42.033	$42.03	$42.05	$42.00
Purchase #4	$140.47	7.376%	$150.8311	$150.83	$150.85	$150.80
Purchase #5	$10.81	7.630%	$11.6348	$11.63	$11.65	$11.60
Purchase #6	$185.90	5.299%	$195.7508	$195.75	$195.75	$195.80
Purchase #7	$73.33	11.114%	$81.4799	$81.48	$81.50	$81.50
7 purchase totals =	$718.93		$766.9902	$766.98	$767.05	$767.00