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	$31.74	11.799%	$35.485	$35.49	$35.50	$35.50
Purchase #2	$61.94	8.586%	$67.2582	$67.26	$67.25	$67.30
Purchase #3	$210.99	10.675%	$233.5132	$233.51	$233.50	$233.50
Purchase #4	$237.71	12.679%	$267.8493	$267.85	$267.85	$267.80
Purchase #5	$78.68	4.713%	$82.3882	$82.39	$82.40	$82.40
Purchase #6	$166.59	3.451%	$172.339	$172.34	$172.35	$172.30
Purchase #7	$196.83	5.349%	$207.3584	$207.36	$207.35	$207.40
7 purchase totals =	$984.48		$1,066.1913	$1,066.20	$1,066.20	$1,066.20