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	$167.40	3.722%	$173.6306	$173.63	$173.65	$173.60
Purchase #2	$36.71	8.253%	$39.7397	$39.74	$39.75	$39.70
Purchase #3	$201.57	10.421%	$222.5756	$222.58	$222.60	$222.60
Purchase #4	$134.50	5.560%	$141.9782	$141.98	$142.00	$142.00
Purchase #5	$215.95	10.504%	$238.6334	$238.63	$238.65	$238.60
Purchase #6	$241.73	11.810%	$270.2783	$270.28	$270.30	$270.30
Purchase #7	$88.43	13.809%	$100.6413	$100.64	$100.65	$100.60
7 purchase totals =	$1,086.29		$1,187.4771	$1,187.48	$1,187.60	$1,187.40