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	$67.67	6.799%	$72.2709	$72.27	$72.25	$72.30
Purchase #2	$36.63	6.291%	$38.9344	$38.93	$38.95	$38.90
Purchase #3	$14.28	9.335%	$15.613	$15.61	$15.60	$15.60
Purchase #4	$103.59	10.282%	$114.2411	$114.24	$114.25	$114.20
Purchase #5	$45.55	6.636%	$48.5727	$48.57	$48.55	$48.60
Purchase #6	$36.33	7.532%	$39.0664	$39.07	$39.05	$39.10
Purchase #7	$131.73	8.734%	$143.2353	$143.24	$143.25	$143.20
7 purchase totals =	$435.78		$471.9338	$471.93	$471.90	$471.90