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	$70.51	11.388%	$78.5397	$78.54	$78.55	$78.50
Purchase #2	$96.70	5.333%	$101.857	$101.86	$101.85	$101.90
Purchase #3	$104.95	4.246%	$109.4062	$109.41	$109.40	$109.40
Purchase #4	$72.39	5.519%	$76.3852	$76.39	$76.40	$76.40
Purchase #5	$84.72	12.593%	$95.3888	$95.39	$95.40	$95.40
Purchase #6	$54.99	11.206%	$61.1522	$61.15	$61.15	$61.20
Purchase #7	$150.85	11.549%	$168.2717	$168.27	$168.25	$168.30
7 purchase totals =	$635.11		$691.0008	$691.01	$691.00	$691.10