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	$215.96	10.406%	$238.4328	$238.43	$238.45	$238.40
Purchase #2	$6.36	11.648%	$7.1008	$7.10	$7.10	$7.10
Purchase #3	$184.30	3.166%	$190.1349	$190.13	$190.15	$190.10
Purchase #4	$154.32	8.612%	$167.61	$167.61	$167.60	$167.60
Purchase #5	$247.90	8.211%	$268.2551	$268.26	$268.25	$268.30
Purchase #6	$129.39	8.842%	$140.8307	$140.83	$140.85	$140.80
Purchase #7	$68.84	7.410%	$73.941	$73.94	$73.95	$73.90
7 purchase totals =	$1,007.07		$1,086.3053	$1,086.30	$1,086.35	$1,086.20