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	$145.83	7.804%	$157.2106	$157.21	$157.20	$157.20
Purchase #2	$172.73	3.860%	$179.3974	$179.40	$179.40	$179.40
Purchase #3	$81.27	10.769%	$90.022	$90.02	$90.00	$90.00
Purchase #4	$58.40	12.428%	$65.658	$65.66	$65.65	$65.70
Purchase #5	$9.72	3.673%	$10.077	$10.08	$10.10	$10.10
Purchase #6	$180.85	8.834%	$196.8263	$196.83	$196.85	$196.80
Purchase #7	$190.59	8.777%	$207.3181	$207.32	$207.30	$207.30
7 purchase totals =	$839.39		$906.5094	$906.52	$906.50	$906.50