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	$130.30	7.823%	$140.4934	$140.49	$140.50	$140.50
Purchase #2	$85.35	12.389%	$95.924	$95.92	$95.90	$95.90
Purchase #3	$196.64	4.793%	$206.065	$206.07	$206.05	$206.10
Purchase #4	$48.98	9.802%	$53.781	$53.78	$53.80	$53.80
Purchase #5	$13.39	6.318%	$14.236	$14.24	$14.25	$14.20
Purchase #6	$47.35	11.835%	$52.9539	$52.95	$52.95	$53.00
Purchase #7	$203.83	9.330%	$222.8473	$222.85	$222.85	$222.80
7 purchase totals =	$725.84		$786.3006	$786.30	$786.30	$786.30