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	$62.78	12.725%	$70.7688	$70.77	$70.75	$70.80
Purchase #2	$144.35	4.637%	$151.0435	$151.04	$151.05	$151.00
Purchase #3	$162.87	11.705%	$181.9339	$181.93	$181.95	$181.90
Purchase #4	$244.51	5.854%	$258.8236	$258.82	$258.80	$258.80
Purchase #5	$80.96	12.240%	$90.8695	$90.87	$90.85	$90.90
Purchase #6	$244.56	11.752%	$273.3007	$273.30	$273.30	$273.30
Purchase #7	$243.82	10.108%	$268.4653	$268.47	$268.45	$268.50
7 purchase totals =	$1,183.85		$1,295.2053	$1,295.20	$1,295.15	$1,295.20