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	$22.51	8.531%	$24.4303	$24.43	$24.45	$24.40
Purchase #2	$142.46	5.650%	$150.509	$150.51	$150.50	$150.50
Purchase #3	$40.92	6.321%	$43.5066	$43.51	$43.50	$43.50
Purchase #4	$154.29	7.315%	$165.5763	$165.58	$165.60	$165.60
Purchase #5	$23.98	6.369%	$25.5073	$25.51	$25.50	$25.50
Purchase #6	$88.97	8.543%	$96.5707	$96.57	$96.55	$96.60
Purchase #7	$247.40	11.670%	$276.2716	$276.27	$276.25	$276.30
7 purchase totals =	$720.53		$782.3718	$782.38	$782.35	$782.40