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	$237.55	10.681%	$262.9227	$262.92	$262.90	$262.90
Purchase #2	$174.37	8.728%	$189.589	$189.59	$189.60	$189.60
Purchase #3	$22.46	11.533%	$25.0503	$25.05	$25.05	$25.10
Purchase #4	$205.78	4.715%	$215.4825	$215.48	$215.50	$215.50
Purchase #5	$128.32	12.795%	$144.7385	$144.74	$144.75	$144.70
Purchase #6	$114.92	10.652%	$127.1613	$127.16	$127.15	$127.20
Purchase #7	$137.47	13.834%	$156.4876	$156.49	$156.50	$156.50
7 purchase totals =	$1,020.87		$1,121.4319	$1,121.43	$1,121.45	$1,121.50