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	$174.47	5.136%	$183.4308	$183.43	$183.45	$183.40
Purchase #2	$19.69	4.172%	$20.5115	$20.51	$20.50	$20.50
Purchase #3	$210.90	4.347%	$220.0678	$220.07	$220.05	$220.10
Purchase #4	$117.69	8.493%	$127.6854	$127.69	$127.70	$127.70
Purchase #5	$193.61	8.143%	$209.3757	$209.38	$209.40	$209.40
Purchase #6	$154.50	11.403%	$172.1176	$172.12	$172.10	$172.10
Purchase #7	$179.39	4.138%	$186.8132	$186.81	$186.80	$186.80
7 purchase totals =	$1,050.25		$1,120.0020	$1,120.01	$1,120.00	$1,120.00