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	$111.64	6.787%	$119.217	$119.22	$119.20	$119.20
Purchase #2	$99.85	7.414%	$107.2529	$107.25	$107.25	$107.30
Purchase #3	$223.85	12.520%	$251.876	$251.88	$251.90	$251.90
Purchase #4	$159.30	9.858%	$175.0038	$175.00	$175.00	$175.00
Purchase #5	$233.97	8.184%	$253.1181	$253.12	$253.10	$253.10
Purchase #6	$116.56	12.718%	$131.3841	$131.38	$131.40	$131.40
Purchase #7	$153.86	5.616%	$162.5008	$162.50	$162.50	$162.50
7 purchase totals =	$1,099.03		$1,200.3527	$1,200.35	$1,200.35	$1,200.40