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	$216.58	8.670%	$235.3575	$235.36	$235.35	$235.40
Purchase #2	$149.56	10.271%	$164.9213	$164.92	$164.90	$164.90
Purchase #3	$78.95	11.815%	$88.2779	$88.28	$88.30	$88.30
Purchase #4	$82.76	9.473%	$90.5999	$90.60	$90.60	$90.60
Purchase #5	$87.97	3.834%	$91.3428	$91.34	$91.35	$91.30
Purchase #6	$159.47	4.151%	$166.0896	$166.09	$166.10	$166.10
Purchase #7	$218.42	11.479%	$243.4924	$243.49	$243.50	$243.50
7 purchase totals =	$993.71		$1,080.0814	$1,080.08	$1,080.10	$1,080.10