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	$148.76	6.587%	$158.5588	$158.56	$158.55	$158.60
Purchase #2	$132.34	13.223%	$149.8393	$149.84	$149.85	$149.80
Purchase #3	$31.34	13.543%	$35.5844	$35.58	$35.60	$35.60
Purchase #4	$64.57	4.380%	$67.3982	$67.40	$67.40	$67.40
Purchase #5	$94.72	3.596%	$98.1261	$98.13	$98.15	$98.10
Purchase #6	$185.77	3.614%	$192.4837	$192.48	$192.50	$192.50
Purchase #7	$39.40	7.729%	$42.4452	$42.45	$42.45	$42.40
7 purchase totals =	$696.90		$744.4357	$744.44	$744.50	$744.40