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	$164.63	10.167%	$181.3679	$181.37	$181.35	$181.40
Purchase #2	$26.91	12.593%	$30.2988	$30.30	$30.30	$30.30
Purchase #3	$232.73	3.792%	$241.5551	$241.56	$241.55	$241.60
Purchase #4	$164.47	5.119%	$172.8892	$172.89	$172.90	$172.90
Purchase #5	$174.85	12.331%	$196.4108	$196.41	$196.40	$196.40
Purchase #6	$132.70	13.660%	$150.8268	$150.83	$150.85	$150.80
Purchase #7	$247.30	3.188%	$255.1839	$255.18	$255.20	$255.20
7 purchase totals =	$1,143.59		$1,228.5325	$1,228.54	$1,228.55	$1,228.60