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	$68.91	5.117%	$72.4361	$72.44	$72.45	$72.40
Purchase #2	$243.99	12.157%	$273.6519	$273.65	$273.65	$273.70
Purchase #3	$202.67	9.627%	$222.181	$222.18	$222.20	$222.20
Purchase #4	$134.81	3.755%	$139.8721	$139.87	$139.85	$139.90
Purchase #5	$88.97	7.444%	$95.5929	$95.59	$95.60	$95.60
Purchase #6	$107.78	10.610%	$119.2155	$119.22	$119.20	$119.20
Purchase #7	$51.33	6.202%	$54.5135	$54.51	$54.50	$54.50
7 purchase totals =	$898.46		$977.4630	$977.46	$977.45	$977.50