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	$74.75	11.503%	$83.3485	$83.35	$83.35	$83.30
Purchase #2	$127.62	3.316%	$131.8519	$131.85	$131.85	$131.90
Purchase #3	$186.89	12.639%	$210.511	$210.51	$210.50	$210.50
Purchase #4	$100.62	7.633%	$108.3003	$108.30	$108.30	$108.30
Purchase #5	$173.29	6.114%	$183.885	$183.89	$183.90	$183.90
Purchase #6	$234.85	11.700%	$262.3275	$262.33	$262.35	$262.30
Purchase #7	$184.32	11.675%	$205.8394	$205.84	$205.85	$205.80
7 purchase totals =	$1,082.34		$1,186.0636	$1,186.07	$1,186.10	$1,186.00