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	$130.30	10.664%	$144.1952	$144.20	$144.20	$144.20
Purchase #2	$125.57	4.188%	$130.8289	$130.83	$130.85	$130.80
Purchase #3	$224.28	13.874%	$255.3966	$255.40	$255.40	$255.40
Purchase #4	$135.58	7.139%	$145.2591	$145.26	$145.25	$145.30
Purchase #5	$205.58	9.178%	$224.4481	$224.45	$224.45	$224.40
Purchase #6	$138.44	4.213%	$144.2725	$144.27	$144.25	$144.30
Purchase #7	$28.71	12.870%	$32.405	$32.41	$32.40	$32.40
7 purchase totals =	$988.46		$1,076.8054	$1,076.82	$1,076.80	$1,076.80