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	$142.96	5.224%	$150.4282	$150.43	$150.45	$150.40
Purchase #2	$54.69	5.660%	$57.7855	$57.79	$57.80	$57.80
Purchase #3	$125.82	8.170%	$136.0995	$136.10	$136.10	$136.10
Purchase #4	$245.74	11.208%	$273.2825	$273.28	$273.30	$273.30
Purchase #5	$183.66	12.652%	$206.8967	$206.90	$206.90	$206.90
Purchase #6	$134.27	5.119%	$141.1433	$141.14	$141.15	$141.10
Purchase #7	$106.38	12.405%	$119.5764	$119.58	$119.60	$119.60
7 purchase totals =	$993.52		$1,085.2121	$1,085.22	$1,085.30	$1,085.20