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	$101.35	7.763%	$109.2178	$109.22	$109.20	$109.20
Purchase #2	$79.62	11.154%	$88.5008	$88.50	$88.50	$88.50
Purchase #3	$82.72	3.212%	$85.377	$85.38	$85.40	$85.40
Purchase #4	$157.41	9.835%	$172.8913	$172.89	$172.90	$172.90
Purchase #5	$67.48	8.537%	$73.2408	$73.24	$73.25	$73.20
Purchase #6	$50.96	12.808%	$57.487	$57.49	$57.50	$57.50
Purchase #7	$119.83	9.874%	$131.662	$131.66	$131.65	$131.70
7 purchase totals =	$659.37		$718.3767	$718.38	$718.40	$718.40