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	$153.53	8.619%	$166.7628	$166.76	$166.75	$166.80
Purchase #2	$21.79	11.512%	$24.2985	$24.30	$24.30	$24.30
Purchase #3	$5.85	12.669%	$6.5911	$6.59	$6.60	$6.60
Purchase #4	$52.68	6.112%	$55.8998	$55.90	$55.90	$55.90
Purchase #5	$249.89	6.139%	$265.2307	$265.23	$265.25	$265.20
Purchase #6	$123.36	12.844%	$139.2044	$139.20	$139.20	$139.20
Purchase #7	$237.57	7.568%	$255.5493	$255.55	$255.55	$255.50
7 purchase totals =	$844.67		$913.5366	$913.53	$913.55	$913.50