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	$99.35	13.852%	$113.112	$113.11	$113.10	$113.10
Purchase #2	$144.40	3.108%	$148.888	$148.89	$148.90	$148.90
Purchase #3	$216.81	12.763%	$244.4815	$244.48	$244.50	$244.50
Purchase #4	$119.33	3.412%	$123.4015	$123.40	$123.40	$123.40
Purchase #5	$228.54	11.527%	$254.8838	$254.88	$254.90	$254.90
Purchase #6	$76.54	8.378%	$82.9525	$82.95	$82.95	$83.00
Purchase #7	$104.98	3.145%	$108.2816	$108.28	$108.30	$108.30
7 purchase totals =	$989.95		$1,076.0009	$1,075.99	$1,076.05	$1,076.10