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	$91.64	10.833%	$101.5674	$101.57	$101.55	$101.60
Purchase #2	$63.35	4.626%	$66.2806	$66.28	$66.30	$66.30
Purchase #3	$64.59	11.839%	$72.2368	$72.24	$72.25	$72.20
Purchase #4	$34.37	13.140%	$38.8862	$38.89	$38.90	$38.90
Purchase #5	$249.68	9.606%	$273.6643	$273.66	$273.65	$273.70
Purchase #6	$50.81	10.470%	$56.1298	$56.13	$56.15	$56.10
Purchase #7	$10.28	7.818%	$11.0837	$11.08	$11.10	$11.10
7 purchase totals =	$564.72		$619.8488	$619.85	$619.90	$619.90