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	$21.31	6.327%	$22.6583	$22.66	$22.65	$22.70
Purchase #2	$21.25	7.578%	$22.8603	$22.86	$22.85	$22.90
Purchase #3	$170.31	6.806%	$181.9013	$181.90	$181.90	$181.90
Purchase #4	$53.44	6.813%	$57.0809	$57.08	$57.10	$57.10
Purchase #5	$227.25	5.819%	$240.4737	$240.47	$240.45	$240.50
Purchase #6	$90.44	11.420%	$100.7682	$100.77	$100.75	$100.80
Purchase #7	$85.63	4.572%	$89.545	$89.55	$89.55	$89.50
7 purchase totals =	$669.63		$715.2877	$715.29	$715.25	$715.40