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	$10.37	8.463%	$11.2476	$11.25	$11.25	$11.20
Purchase #2	$246.56	6.788%	$263.2965	$263.30	$263.30	$263.30
Purchase #3	$35.65	12.623%	$40.1501	$40.15	$40.15	$40.20
Purchase #4	$227.97	4.510%	$238.2514	$238.25	$238.25	$238.30
Purchase #5	$28.34	9.570%	$31.0521	$31.05	$31.05	$31.10
Purchase #6	$51.88	13.861%	$59.0711	$59.07	$59.05	$59.10
Purchase #7	$208.97	10.796%	$231.5304	$231.53	$231.55	$231.50
7 purchase totals =	$809.74		$874.5992	$874.60	$874.60	$874.70