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	$148.28	13.252%	$167.9301	$167.93	$167.95	$167.90
Purchase #2	$177.89	7.738%	$191.6551	$191.66	$191.65	$191.70
Purchase #3	$64.38	8.344%	$69.7519	$69.75	$69.75	$69.80
Purchase #4	$126.84	3.621%	$131.4329	$131.43	$131.45	$131.40
Purchase #5	$222.62	7.748%	$239.8686	$239.87	$239.85	$239.90
Purchase #6	$99.60	4.820%	$104.4007	$104.40	$104.40	$104.40
Purchase #7	$108.90	3.177%	$112.3598	$112.36	$112.35	$112.40
7 purchase totals =	$948.51		$1,017.3991	$1,017.40	$1,017.40	$1,017.50