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	$175.33	5.570%	$185.0959	$185.10	$185.10	$185.10
Purchase #2	$220.86	7.766%	$238.012	$238.01	$238.00	$238.00
Purchase #3	$169.83	10.518%	$187.6927	$187.69	$187.70	$187.70
Purchase #4	$107.93	4.597%	$112.8915	$112.89	$112.90	$112.90
Purchase #5	$54.84	6.736%	$58.534	$58.53	$58.55	$58.50
Purchase #6	$154.49	11.372%	$172.0586	$172.06	$172.05	$172.10
Purchase #7	$91.46	3.577%	$94.7315	$94.73	$94.75	$94.70
7 purchase totals =	$974.74		$1,049.0162	$1,049.01	$1,049.05	$1,049.00