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	$155.28	8.250%	$168.0906	$168.09	$168.10	$168.10
Purchase #2	$96.52	13.496%	$109.5463	$109.55	$109.55	$109.50
Purchase #3	$224.85	7.397%	$241.4822	$241.48	$241.50	$241.50
Purchase #4	$102.53	4.162%	$106.7973	$106.80	$106.80	$106.80
Purchase #5	$213.38	3.849%	$221.593	$221.59	$221.60	$221.60
Purchase #6	$75.79	3.454%	$78.4078	$78.41	$78.40	$78.40
Purchase #7	$91.69	7.821%	$98.8611	$98.86	$98.85	$98.90
7 purchase totals =	$960.04		$1,024.7783	$1,024.78	$1,024.80	$1,024.80