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	$12.75	10.575%	$14.0983	$14.10	$14.10	$14.10
Purchase #2	$35.53	5.708%	$37.5581	$37.56	$37.55	$37.60
Purchase #3	$31.60	7.167%	$33.8648	$33.86	$33.85	$33.90
Purchase #4	$134.86	7.745%	$145.3049	$145.30	$145.30	$145.30
Purchase #5	$215.66	12.444%	$242.4967	$242.50	$242.50	$242.50
Purchase #6	$189.61	11.235%	$210.9127	$210.91	$210.90	$210.90
Purchase #7	$128.28	13.495%	$145.5914	$145.59	$145.60	$145.60
7 purchase totals =	$748.29		$829.8269	$829.82	$829.80	$829.90