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	$152.65	6.731%	$162.9249	$162.92	$162.90	$162.90
Purchase #2	$221.67	6.269%	$235.5665	$235.57	$235.55	$235.60
Purchase #3	$176.43	10.583%	$195.1016	$195.10	$195.10	$195.10
Purchase #4	$238.84	3.172%	$246.416	$246.42	$246.40	$246.40
Purchase #5	$42.41	8.170%	$45.8749	$45.87	$45.85	$45.90
Purchase #6	$82.41	9.379%	$90.1392	$90.14	$90.15	$90.10
Purchase #7	$116.46	3.149%	$120.1273	$120.13	$120.15	$120.10
7 purchase totals =	$1,030.87		$1,096.1504	$1,096.15	$1,096.10	$1,096.10