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	$229.94	13.153%	$260.184	$260.18	$260.20	$260.20
Purchase #2	$168.52	4.231%	$175.6501	$175.65	$175.65	$175.70
Purchase #3	$40.45	4.130%	$42.1206	$42.12	$42.10	$42.10
Purchase #4	$81.30	10.506%	$89.8414	$89.84	$89.85	$89.80
Purchase #5	$113.91	5.161%	$119.7889	$119.79	$119.80	$119.80
Purchase #6	$112.68	10.154%	$124.1215	$124.12	$124.10	$124.10
Purchase #7	$153.36	7.431%	$164.7562	$164.76	$164.75	$164.80
7 purchase totals =	$900.16		$976.4627	$976.46	$976.45	$976.50