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	$107.92	10.844%	$119.6228	$119.62	$119.60	$119.60
Purchase #2	$84.63	7.738%	$91.1787	$91.18	$91.20	$91.20
Purchase #3	$38.37	5.592%	$40.5157	$40.52	$40.50	$40.50
Purchase #4	$154.79	12.359%	$173.9205	$173.92	$173.90	$173.90
Purchase #5	$9.84	12.873%	$11.1067	$11.11	$11.10	$11.10
Purchase #6	$161.44	3.732%	$167.4649	$167.46	$167.45	$167.50
Purchase #7	$186.40	5.374%	$196.4171	$196.42	$196.40	$196.40
7 purchase totals =	$743.39		$800.2264	$800.23	$800.15	$800.20