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	$106.49	11.785%	$119.0398	$119.04	$119.05	$119.00
Purchase #2	$27.37	3.613%	$28.3589	$28.36	$28.35	$28.40
Purchase #3	$116.49	12.478%	$131.0256	$131.03	$131.05	$131.00
Purchase #4	$242.61	8.157%	$262.3997	$262.40	$262.40	$262.40
Purchase #5	$65.31	9.592%	$71.5745	$71.57	$71.55	$71.60
Purchase #6	$106.74	5.272%	$112.3673	$112.37	$112.35	$112.40
Purchase #7	$87.70	3.388%	$90.6713	$90.67	$90.65	$90.70
7 purchase totals =	$752.71		$815.4371	$815.44	$815.40	$815.50