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	$64.94	11.250%	$72.2458	$72.25	$72.25	$72.20
Purchase #2	$171.96	9.528%	$188.3443	$188.34	$188.35	$188.30
Purchase #3	$18.36	8.496%	$19.9199	$19.92	$19.90	$19.90
Purchase #4	$43.66	8.264%	$47.2681	$47.27	$47.25	$47.30
Purchase #5	$91.94	11.466%	$102.4818	$102.48	$102.50	$102.50
Purchase #6	$151.63	4.418%	$158.329	$158.33	$158.35	$158.30
Purchase #7	$19.58	8.801%	$21.3032	$21.30	$21.30	$21.30
7 purchase totals =	$562.07		$609.8921	$609.89	$609.90	$609.80