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	$185.51	13.276%	$210.1383	$210.14	$210.15	$210.10
Purchase #2	$236.25	9.311%	$258.2472	$258.25	$258.25	$258.20
Purchase #3	$210.82	3.697%	$218.614	$218.61	$218.60	$218.60
Purchase #4	$106.88	13.322%	$121.1186	$121.12	$121.10	$121.10
Purchase #5	$52.38	13.623%	$59.5157	$59.52	$59.50	$59.50
Purchase #6	$20.89	7.811%	$22.5217	$22.52	$22.50	$22.50
Purchase #7	$213.42	13.156%	$241.4975	$241.50	$241.50	$241.50
7 purchase totals =	$1,026.15		$1,131.6530	$1,131.66	$1,131.60	$1,131.50