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	$150.34	7.410%	$161.4802	$161.48	$161.50	$161.50
Purchase #2	$98.36	13.249%	$111.3917	$111.39	$111.40	$111.40
Purchase #3	$113.69	11.833%	$127.1429	$127.14	$127.15	$127.10
Purchase #4	$28.99	4.233%	$30.2171	$30.22	$30.20	$30.20
Purchase #5	$54.52	4.349%	$56.8911	$56.89	$56.90	$56.90
Purchase #6	$207.73	4.807%	$217.7156	$217.72	$217.70	$217.70
Purchase #7	$241.67	12.696%	$272.3524	$272.35	$272.35	$272.40
7 purchase totals =	$895.30		$977.1910	$977.19	$977.20	$977.20