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	$162.85	12.659%	$183.4652	$183.47	$183.45	$183.50
Purchase #2	$126.97	3.404%	$131.2921	$131.29	$131.30	$131.30
Purchase #3	$218.29	11.551%	$243.5047	$243.50	$243.50	$243.50
Purchase #4	$168.26	7.210%	$180.3915	$180.39	$180.40	$180.40
Purchase #5	$73.87	12.571%	$83.1562	$83.16	$83.15	$83.20
Purchase #6	$30.87	3.123%	$31.8341	$31.83	$31.85	$31.80
Purchase #7	$216.88	3.123%	$223.6532	$223.65	$223.65	$223.70
7 purchase totals =	$997.99		$1,077.2970	$1,077.29	$1,077.30	$1,077.40