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	$77.97	11.441%	$86.8905	$86.89	$86.90	$86.90
Purchase #2	$243.32	6.191%	$258.3839	$258.38	$258.40	$258.40
Purchase #3	$97.86	5.454%	$103.1973	$103.20	$103.20	$103.20
Purchase #4	$36.46	3.175%	$37.6176	$37.62	$37.60	$37.60
Purchase #5	$173.94	9.736%	$190.8748	$190.87	$190.85	$190.90
Purchase #6	$124.55	10.141%	$137.1806	$137.18	$137.20	$137.20
Purchase #7	$29.90	6.358%	$31.801	$31.80	$31.80	$31.80
7 purchase totals =	$784.00		$845.9457	$845.94	$845.95	$846.00