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	$104.55	8.105%	$113.0238	$113.02	$113.00	$113.00
Purchase #2	$94.98	5.566%	$100.2666	$100.27	$100.25	$100.30
Purchase #3	$83.80	6.813%	$89.5093	$89.51	$89.50	$89.50
Purchase #4	$31.54	13.360%	$35.7537	$35.75	$35.75	$35.80
Purchase #5	$8.74	13.682%	$9.9358	$9.94	$9.95	$9.90
Purchase #6	$77.67	4.780%	$81.3826	$81.38	$81.40	$81.40
Purchase #7	$133.77	6.651%	$142.667	$142.67	$142.65	$142.70
7 purchase totals =	$535.05		$572.5388	$572.54	$572.50	$572.60