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	$97.25	3.336%	$100.4943	$100.49	$100.50	$100.50
Purchase #2	$214.94	3.443%	$222.3404	$222.34	$222.35	$222.30
Purchase #3	$102.30	5.408%	$107.8324	$107.83	$107.85	$107.80
Purchase #4	$86.94	4.427%	$90.7888	$90.79	$90.80	$90.80
Purchase #5	$207.32	4.472%	$216.5914	$216.59	$216.60	$216.60
Purchase #6	$170.99	5.599%	$180.5637	$180.56	$180.55	$180.60
Purchase #7	$182.28	6.112%	$193.421	$193.42	$193.40	$193.40
7 purchase totals =	$1,062.02		$1,112.0320	$1,112.02	$1,112.05	$1,112.00