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	$216.74	4.736%	$227.0048	$227.00	$227.00	$227.00
Purchase #2	$35.78	5.601%	$37.784	$37.78	$37.80	$37.80
Purchase #3	$52.49	13.653%	$59.6565	$59.66	$59.65	$59.70
Purchase #4	$198.89	4.858%	$208.5521	$208.55	$208.55	$208.60
Purchase #5	$61.66	13.231%	$69.8182	$69.82	$69.80	$69.80
Purchase #6	$158.83	5.665%	$167.8277	$167.83	$167.85	$167.80
Purchase #7	$54.84	4.553%	$57.3369	$57.34	$57.35	$57.30
7 purchase totals =	$779.23		$827.9802	$827.98	$828.00	$828.00