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	$31.83	4.732%	$33.3362	$33.34	$33.35	$33.30
Purchase #2	$44.73	13.428%	$50.7363	$50.74	$50.75	$50.70
Purchase #3	$167.98	13.439%	$190.5548	$190.55	$190.55	$190.60
Purchase #4	$29.83	8.854%	$32.4711	$32.47	$32.45	$32.50
Purchase #5	$109.92	3.783%	$114.0783	$114.08	$114.10	$114.10
Purchase #6	$141.83	3.150%	$146.2976	$146.30	$146.30	$146.30
Purchase #7	$116.34	7.764%	$125.3726	$125.37	$125.35	$125.40
7 purchase totals =	$642.46		$692.8469	$692.85	$692.85	$692.90