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	$150.86	3.519%	$156.1688	$156.17	$156.15	$156.20
Purchase #2	$18.70	5.558%	$19.7393	$19.74	$19.75	$19.70
Purchase #3	$196.38	4.320%	$204.8636	$204.86	$204.85	$204.90
Purchase #4	$17.46	12.264%	$19.6013	$19.60	$19.60	$19.60
Purchase #5	$62.56	8.406%	$67.8188	$67.82	$67.80	$67.80
Purchase #6	$69.41	12.448%	$78.0502	$78.05	$78.05	$78.10
Purchase #7	$151.71	11.775%	$169.5739	$169.57	$169.55	$169.60
7 purchase totals =	$667.08		$715.8159	$715.81	$715.75	$715.90