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	$243.64	8.106%	$263.3895	$263.39	$263.40	$263.40
Purchase #2	$48.49	7.282%	$52.021	$52.02	$52.00	$52.00
Purchase #3	$57.56	3.337%	$59.4808	$59.48	$59.50	$59.50
Purchase #4	$95.71	7.794%	$103.1696	$103.17	$103.15	$103.20
Purchase #5	$53.56	12.656%	$60.3386	$60.34	$60.35	$60.30
Purchase #6	$186.58	4.788%	$195.5135	$195.51	$195.50	$195.50
Purchase #7	$228.40	8.856%	$248.6271	$248.63	$248.65	$248.60
7 purchase totals =	$913.94		$982.5401	$982.54	$982.55	$982.50