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	$193.95	13.223%	$219.596	$219.60	$219.60	$219.60
Purchase #2	$158.52	5.109%	$166.6188	$166.62	$166.60	$166.60
Purchase #3	$35.95	3.294%	$37.1342	$37.13	$37.15	$37.10
Purchase #4	$204.50	4.279%	$213.2506	$213.25	$213.25	$213.30
Purchase #5	$156.25	12.269%	$175.4203	$175.42	$175.40	$175.40
Purchase #6	$184.85	3.853%	$191.9723	$191.97	$191.95	$192.00
Purchase #7	$149.59	12.541%	$168.3501	$168.35	$168.35	$168.40
7 purchase totals =	$1,083.61		$1,172.3423	$1,172.34	$1,172.30	$1,172.40