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	$82.29	4.510%	$86.0013	$86.00	$86.00	$86.00
Purchase #2	$48.81	5.861%	$51.6708	$51.67	$51.65	$51.70
Purchase #3	$55.26	3.627%	$57.2643	$57.26	$57.25	$57.30
Purchase #4	$189.85	13.852%	$216.148	$216.15	$216.15	$216.10
Purchase #5	$250.27	9.386%	$273.7603	$273.76	$273.75	$273.80
Purchase #6	$102.41	11.577%	$114.266	$114.27	$114.25	$114.30
Purchase #7	$249.30	12.388%	$280.1833	$280.18	$280.20	$280.20
7 purchase totals =	$978.19		$1,079.2940	$1,079.29	$1,079.25	$1,079.40