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	$163.50	3.325%	$168.9364	$168.94	$168.95	$168.90
Purchase #2	$186.48	3.741%	$193.4562	$193.46	$193.45	$193.50
Purchase #3	$156.54	9.402%	$171.2579	$171.26	$171.25	$171.30
Purchase #4	$6.98	7.588%	$7.5096	$7.51	$7.50	$7.50
Purchase #5	$241.56	13.169%	$273.371	$273.37	$273.35	$273.40
Purchase #6	$55.95	5.751%	$59.1677	$59.17	$59.15	$59.20
Purchase #7	$11.50	10.211%	$12.6743	$12.67	$12.65	$12.70
7 purchase totals =	$822.51		$886.3731	$886.38	$886.30	$886.50