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	$115.64	10.238%	$127.4792	$127.48	$127.50	$127.50
Purchase #2	$41.64	10.182%	$45.8798	$45.88	$45.90	$45.90
Purchase #3	$137.94	13.703%	$156.8419	$156.84	$156.85	$156.80
Purchase #4	$161.83	13.183%	$183.164	$183.16	$183.15	$183.20
Purchase #5	$35.82	12.586%	$40.3283	$40.33	$40.35	$40.30
Purchase #6	$151.88	5.874%	$160.8014	$160.80	$160.80	$160.80
Purchase #7	$192.46	5.408%	$202.8682	$202.87	$202.85	$202.90
7 purchase totals =	$837.21		$917.3628	$917.36	$917.40	$917.40