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	$39.29	6.695%	$41.9205	$41.92	$41.90	$41.90
Purchase #2	$68.56	5.151%	$72.0915	$72.09	$72.10	$72.10
Purchase #3	$118.99	9.620%	$130.4368	$130.44	$130.45	$130.40
Purchase #4	$246.67	13.317%	$279.519	$279.52	$279.50	$279.50
Purchase #5	$197.98	12.558%	$222.8423	$222.84	$222.85	$222.80
Purchase #6	$81.79	13.123%	$92.5233	$92.52	$92.50	$92.50
Purchase #7	$208.75	13.109%	$236.115	$236.12	$236.10	$236.10
7 purchase totals =	$962.03		$1,075.4484	$1,075.45	$1,075.40	$1,075.30