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	$116.65	4.205%	$121.5551	$121.56	$121.55	$121.60
Purchase #2	$227.50	7.508%	$244.5807	$244.58	$244.60	$244.60
Purchase #3	$211.60	5.292%	$222.7979	$222.80	$222.80	$222.80
Purchase #4	$68.96	7.142%	$73.8851	$73.89	$73.90	$73.90
Purchase #5	$161.42	3.397%	$166.9034	$166.90	$166.90	$166.90
Purchase #6	$225.71	12.807%	$254.6167	$254.62	$254.60	$254.60
Purchase #7	$35.57	13.804%	$40.4801	$40.48	$40.50	$40.50
7 purchase totals =	$1,047.41		$1,124.8190	$1,124.83	$1,124.85	$1,124.90