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	$185.44	5.640%	$195.8988	$195.90	$195.90	$195.90
Purchase #2	$225.66	9.139%	$246.2831	$246.28	$246.30	$246.30
Purchase #3	$132.50	13.571%	$150.4816	$150.48	$150.50	$150.50
Purchase #4	$114.90	7.720%	$123.7703	$123.77	$123.75	$123.80
Purchase #5	$111.61	5.235%	$117.4528	$117.45	$117.45	$117.50
Purchase #6	$35.62	13.110%	$40.2898	$40.29	$40.30	$40.30
Purchase #7	$167.38	12.174%	$187.7568	$187.76	$187.75	$187.80
7 purchase totals =	$973.11		$1,061.9332	$1,061.93	$1,061.95	$1,062.10