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	$140.87	11.339%	$156.8432	$156.84	$156.85	$156.80
Purchase #2	$237.79	7.461%	$255.5315	$255.53	$255.55	$255.50
Purchase #3	$36.35	4.176%	$37.868	$37.87	$37.85	$37.90
Purchase #4	$131.76	10.191%	$145.1877	$145.19	$145.20	$145.20
Purchase #5	$185.57	5.508%	$195.7912	$195.79	$195.80	$195.80
Purchase #6	$109.97	7.149%	$117.8318	$117.83	$117.85	$117.80
Purchase #7	$240.33	10.361%	$265.2306	$265.23	$265.25	$265.20
7 purchase totals =	$1,082.64		$1,174.2840	$1,174.28	$1,174.35	$1,174.20