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	$238.90	9.402%	$261.3614	$261.36	$261.35	$261.40
Purchase #2	$241.94	7.749%	$260.6879	$260.69	$260.70	$260.70
Purchase #3	$200.84	12.461%	$225.8667	$225.87	$225.85	$225.90
Purchase #4	$151.50	13.731%	$172.3025	$172.30	$172.30	$172.30
Purchase #5	$85.74	4.862%	$89.9087	$89.91	$89.90	$89.90
Purchase #6	$54.46	7.209%	$58.386	$58.39	$58.40	$58.40
Purchase #7	$132.86	6.761%	$141.8427	$141.84	$141.85	$141.80
7 purchase totals =	$1,106.24		$1,210.3559	$1,210.36	$1,210.35	$1,210.40