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	$165.60	8.483%	$179.6478	$179.65	$179.65	$179.60
Purchase #2	$33.93	7.812%	$36.5806	$36.58	$36.60	$36.60
Purchase #3	$29.80	11.664%	$33.2759	$33.28	$33.30	$33.30
Purchase #4	$35.83	8.687%	$38.9426	$38.94	$38.95	$38.90
Purchase #5	$33.55	13.583%	$38.1071	$38.11	$38.10	$38.10
Purchase #6	$153.66	7.303%	$164.8818	$164.88	$164.90	$164.90
Purchase #7	$146.33	11.289%	$162.8492	$162.85	$162.85	$162.80
7 purchase totals =	$598.70		$654.2850	$654.29	$654.35	$654.20