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	$94.71	13.712%	$107.6966	$107.70	$107.70	$107.70
Purchase #2	$165.33	13.116%	$187.0147	$187.01	$187.00	$187.00
Purchase #3	$168.40	10.545%	$186.1578	$186.16	$186.15	$186.20
Purchase #4	$111.40	5.348%	$117.3577	$117.36	$117.35	$117.40
Purchase #5	$118.37	4.430%	$123.6138	$123.61	$123.60	$123.60
Purchase #6	$32.83	7.155%	$35.179	$35.18	$35.20	$35.20
Purchase #7	$98.29	10.342%	$108.4552	$108.46	$108.45	$108.50
7 purchase totals =	$789.33		$865.4748	$865.48	$865.45	$865.60