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	$159.43	8.406%	$172.8317	$172.83	$172.85	$172.80
Purchase #2	$55.43	5.295%	$58.365	$58.37	$58.35	$58.40
Purchase #3	$9.87	13.627%	$11.215	$11.22	$11.20	$11.20
Purchase #4	$246.56	13.869%	$280.7554	$280.76	$280.75	$280.80
Purchase #5	$98.85	11.779%	$110.4935	$110.49	$110.50	$110.50
Purchase #6	$192.65	3.854%	$200.0747	$200.07	$200.05	$200.10
Purchase #7	$240.54	11.303%	$267.7282	$267.73	$267.75	$267.70
7 purchase totals =	$1,003.33		$1,101.4635	$1,101.47	$1,101.45	$1,101.50