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	$142.66	5.270%	$150.1782	$150.18	$150.20	$150.20
Purchase #2	$248.74	9.580%	$272.5693	$272.57	$272.55	$272.60
Purchase #3	$205.91	5.134%	$216.4814	$216.48	$216.50	$216.50
Purchase #4	$239.40	3.376%	$247.4821	$247.48	$247.50	$247.50
Purchase #5	$38.90	4.854%	$40.7882	$40.79	$40.80	$40.80
Purchase #6	$167.26	5.521%	$176.4944	$176.49	$176.50	$176.50
Purchase #7	$39.89	7.431%	$42.8542	$42.85	$42.85	$42.90
7 purchase totals =	$1,082.76		$1,146.8478	$1,146.84	$1,146.90	$1,147.00