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	$107.42	9.323%	$117.4348	$117.43	$117.45	$117.40
Purchase #2	$61.80	9.700%	$67.7946	$67.79	$67.80	$67.80
Purchase #3	$98.67	12.629%	$111.131	$111.13	$111.15	$111.10
Purchase #4	$156.56	9.288%	$171.1013	$171.10	$171.10	$171.10
Purchase #5	$244.51	12.401%	$274.8317	$274.83	$274.85	$274.80
Purchase #6	$82.58	7.293%	$88.6026	$88.60	$88.60	$88.60
Purchase #7	$33.77	7.626%	$36.3453	$36.35	$36.35	$36.30
7 purchase totals =	$785.31		$867.2413	$867.23	$867.30	$867.10