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	$72.25	5.312%	$76.0879	$76.09	$76.10	$76.10
Purchase #2	$200.44	3.215%	$206.8841	$206.88	$206.90	$206.90
Purchase #3	$64.59	3.298%	$66.7202	$66.72	$66.70	$66.70
Purchase #4	$116.59	3.752%	$120.9645	$120.96	$120.95	$121.00
Purchase #5	$127.63	11.662%	$142.5142	$142.51	$142.50	$142.50
Purchase #6	$159.85	13.663%	$181.6903	$181.69	$181.70	$181.70
Purchase #7	$138.91	3.357%	$143.5732	$143.57	$143.55	$143.60
7 purchase totals =	$880.26		$938.4344	$938.42	$938.40	$938.50