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	$196.45	9.219%	$214.5607	$214.56	$214.55	$214.60
Purchase #2	$41.90	7.789%	$45.1636	$45.16	$45.15	$45.20
Purchase #3	$230.39	4.198%	$240.0618	$240.06	$240.05	$240.10
Purchase #4	$29.81	6.860%	$31.855	$31.86	$31.85	$31.90
Purchase #5	$36.33	4.491%	$37.9616	$37.96	$37.95	$38.00
Purchase #6	$107.59	12.212%	$120.7289	$120.73	$120.75	$120.70
Purchase #7	$160.51	12.250%	$180.1725	$180.17	$180.15	$180.20
7 purchase totals =	$802.98		$870.5041	$870.50	$870.45	$870.70