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	$69.52	12.241%	$78.0299	$78.03	$78.05	$78.00
Purchase #2	$235.33	12.800%	$265.4522	$265.45	$265.45	$265.50
Purchase #3	$141.57	5.103%	$148.7943	$148.79	$148.80	$148.80
Purchase #4	$141.37	10.820%	$156.6662	$156.67	$156.65	$156.70
Purchase #5	$120.54	10.463%	$133.1521	$133.15	$133.15	$133.20
Purchase #6	$169.40	6.363%	$180.1789	$180.18	$180.20	$180.20
Purchase #7	$134.63	11.648%	$150.3117	$150.31	$150.30	$150.30
7 purchase totals =	$1,012.36		$1,112.5853	$1,112.58	$1,112.60	$1,112.70