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	$202.43	11.207%	$225.1163	$225.12	$225.10	$225.10
Purchase #2	$19.86	3.468%	$20.5487	$20.55	$20.55	$20.50
Purchase #3	$192.80	8.128%	$208.4708	$208.47	$208.45	$208.50
Purchase #4	$26.63	4.447%	$27.8142	$27.81	$27.80	$27.80
Purchase #5	$187.53	4.866%	$196.6552	$196.66	$196.65	$196.70
Purchase #6	$158.48	8.137%	$171.3755	$171.38	$171.40	$171.40
Purchase #7	$211.66	12.629%	$238.3905	$238.39	$238.40	$238.40
7 purchase totals =	$999.39		$1,088.3712	$1,088.38	$1,088.35	$1,088.40