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	$141.55	7.225%	$151.777	$151.78	$151.80	$151.80
Purchase #2	$40.93	3.650%	$42.4239	$42.42	$42.40	$42.40
Purchase #3	$30.38	6.175%	$32.256	$32.26	$32.25	$32.30
Purchase #4	$153.25	6.260%	$162.8435	$162.84	$162.85	$162.80
Purchase #5	$13.75	4.275%	$14.3378	$14.34	$14.35	$14.30
Purchase #6	$6.85	6.110%	$7.2685	$7.27	$7.25	$7.30
Purchase #7	$195.63	11.554%	$218.2331	$218.23	$218.25	$218.20
7 purchase totals =	$582.34		$629.1398	$629.14	$629.15	$629.10