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	$172.80	10.155%	$190.3478	$190.35	$190.35	$190.30
Purchase #2	$133.46	13.190%	$151.0634	$151.06	$151.05	$151.10
Purchase #3	$123.35	10.780%	$136.6471	$136.65	$136.65	$136.60
Purchase #4	$118.48	11.663%	$132.2983	$132.30	$132.30	$132.30
Purchase #5	$247.84	5.273%	$260.9086	$260.91	$260.90	$260.90
Purchase #6	$73.75	9.444%	$80.715	$80.72	$80.70	$80.70
Purchase #7	$50.35	5.193%	$52.9647	$52.96	$52.95	$53.00
7 purchase totals =	$920.03		$1,004.9449	$1,004.95	$1,004.90	$1,004.90