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	$141.67	3.353%	$146.4202	$146.42	$146.40	$146.40
Purchase #2	$166.57	9.610%	$182.5774	$182.58	$182.60	$182.60
Purchase #3	$103.62	5.514%	$109.3336	$109.33	$109.35	$109.30
Purchase #4	$133.68	3.122%	$137.8535	$137.85	$137.85	$137.90
Purchase #5	$35.88	12.274%	$40.2839	$40.28	$40.30	$40.30
Purchase #6	$65.40	11.146%	$72.6895	$72.69	$72.70	$72.70
Purchase #7	$32.90	10.555%	$36.3726	$36.37	$36.35	$36.40
7 purchase totals =	$679.72		$725.5307	$725.52	$725.55	$725.60