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	$142.84	4.692%	$149.5421	$149.54	$149.55	$149.50
Purchase #2	$151.68	5.854%	$160.5593	$160.56	$160.55	$160.60
Purchase #3	$99.69	12.562%	$112.2131	$112.21	$112.20	$112.20
Purchase #4	$151.40	10.139%	$166.7504	$166.75	$166.75	$166.80
Purchase #5	$83.81	8.300%	$90.7662	$90.77	$90.75	$90.80
Purchase #6	$187.79	12.677%	$211.5961	$211.60	$211.60	$211.60
Purchase #7	$156.57	10.301%	$172.6983	$172.70	$172.70	$172.70
7 purchase totals =	$973.78		$1,064.1255	$1,064.13	$1,064.10	$1,064.20