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	$86.85	13.695%	$98.7441	$98.74	$98.75	$98.70
Purchase #2	$49.50	10.328%	$54.6124	$54.61	$54.60	$54.60
Purchase #3	$58.90	4.365%	$61.471	$61.47	$61.45	$61.50
Purchase #4	$218.75	6.358%	$232.6581	$232.66	$232.65	$232.70
Purchase #5	$216.25	6.291%	$229.8543	$229.85	$229.85	$229.90
Purchase #6	$144.72	4.262%	$150.888	$150.89	$150.90	$150.90
Purchase #7	$79.85	7.724%	$86.0176	$86.02	$86.00	$86.00
7 purchase totals =	$854.82		$914.2455	$914.24	$914.20	$914.30