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	$69.78	4.484%	$72.9089	$72.91	$72.90	$72.90
Purchase #2	$150.60	5.301%	$158.5833	$158.58	$158.60	$158.60
Purchase #3	$233.43	5.575%	$246.4437	$246.44	$246.45	$246.40
Purchase #4	$206.96	10.391%	$228.4652	$228.47	$228.45	$228.50
Purchase #5	$153.40	6.761%	$163.7714	$163.77	$163.75	$163.80
Purchase #6	$35.32	6.119%	$37.4812	$37.48	$37.50	$37.50
Purchase #7	$233.73	10.839%	$259.064	$259.06	$259.05	$259.10
7 purchase totals =	$1,083.22		$1,166.7177	$1,166.71	$1,166.70	$1,166.80