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	$99.75	5.755%	$105.4906	$105.49	$105.50	$105.50
Purchase #2	$105.89	6.442%	$112.7114	$112.71	$112.70	$112.70
Purchase #3	$50.81	9.478%	$55.6258	$55.63	$55.65	$55.60
Purchase #4	$78.63	6.553%	$83.7826	$83.78	$83.80	$83.80
Purchase #5	$32.94	12.319%	$36.9979	$37.00	$37.00	$37.00
Purchase #6	$151.74	5.831%	$160.588	$160.59	$160.60	$160.60
Purchase #7	$168.82	12.508%	$189.936	$189.94	$189.95	$189.90
7 purchase totals =	$688.58		$745.1323	$745.14	$745.20	$745.10