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	$110.89	11.284%	$123.4028	$123.40	$123.40	$123.40
Purchase #2	$54.90	11.681%	$61.3129	$61.31	$61.30	$61.30
Purchase #3	$215.89	7.481%	$232.0407	$232.04	$232.05	$232.00
Purchase #4	$237.50	7.572%	$255.4835	$255.48	$255.50	$255.50
Purchase #5	$12.31	13.491%	$13.9707	$13.97	$13.95	$14.00
Purchase #6	$87.71	10.318%	$96.7599	$96.76	$96.75	$96.80
Purchase #7	$196.70	8.622%	$213.6595	$213.66	$213.65	$213.70
7 purchase totals =	$915.90		$996.6300	$996.62	$996.60	$996.70