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	$140.82	8.635%	$152.9798	$152.98	$153.00	$153.00
Purchase #2	$10.34	12.181%	$11.5995	$11.60	$11.60	$11.60
Purchase #3	$136.95	8.250%	$148.2484	$148.25	$148.25	$148.20
Purchase #4	$50.59	6.661%	$53.9598	$53.96	$53.95	$54.00
Purchase #5	$134.32	6.867%	$143.5438	$143.54	$143.55	$143.50
Purchase #6	$214.43	13.468%	$243.3094	$243.31	$243.30	$243.30
Purchase #7	$148.91	12.469%	$167.4776	$167.48	$167.50	$167.50
7 purchase totals =	$836.36		$921.1183	$921.12	$921.15	$921.10