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	$177.57	3.715%	$184.1667	$184.17	$184.15	$184.20
Purchase #2	$22.89	3.600%	$23.714	$23.71	$23.70	$23.70
Purchase #3	$90.69	5.719%	$95.8766	$95.88	$95.90	$95.90
Purchase #4	$105.85	10.663%	$117.1368	$117.14	$117.15	$117.10
Purchase #5	$90.67	9.401%	$99.1939	$99.19	$99.20	$99.20
Purchase #6	$239.89	4.468%	$250.6083	$250.61	$250.60	$250.60
Purchase #7	$32.32	6.386%	$34.384	$34.38	$34.40	$34.40
7 purchase totals =	$759.88		$805.0803	$805.08	$805.10	$805.10