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	$153.42	11.483%	$171.0372	$171.04	$171.05	$171.00
Purchase #2	$98.62	5.361%	$103.907	$103.91	$103.90	$103.90
Purchase #3	$172.33	6.474%	$183.4866	$183.49	$183.50	$183.50
Purchase #4	$155.42	10.703%	$172.0546	$172.05	$172.05	$172.10
Purchase #5	$217.30	9.704%	$238.3868	$238.39	$238.40	$238.40
Purchase #6	$162.91	13.548%	$184.981	$184.98	$185.00	$185.00
Purchase #7	$175.38	8.509%	$190.3031	$190.30	$190.30	$190.30
7 purchase totals =	$1,135.38		$1,244.1563	$1,244.16	$1,244.20	$1,244.20