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	$178.94	9.542%	$196.0145	$196.01	$196.00	$196.00
Purchase #2	$130.89	12.480%	$147.2251	$147.23	$147.25	$147.20
Purchase #3	$237.55	7.393%	$255.1121	$255.11	$255.10	$255.10
Purchase #4	$96.87	10.729%	$107.2632	$107.26	$107.25	$107.30
Purchase #5	$25.82	6.652%	$27.5375	$27.54	$27.55	$27.50
Purchase #6	$107.51	8.629%	$116.787	$116.79	$116.80	$116.80
Purchase #7	$103.32	5.811%	$109.3239	$109.32	$109.30	$109.30
7 purchase totals =	$880.90		$959.2633	$959.26	$959.25	$959.20