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	$92.43	4.788%	$96.8555	$96.86	$96.85	$96.90
Purchase #2	$182.51	4.527%	$190.7722	$190.77	$190.75	$190.80
Purchase #3	$46.93	7.648%	$50.5192	$50.52	$50.50	$50.50
Purchase #4	$241.46	8.549%	$262.1024	$262.10	$262.10	$262.10
Purchase #5	$130.69	8.371%	$141.6301	$141.63	$141.65	$141.60
Purchase #6	$164.34	4.348%	$171.4855	$171.49	$171.50	$171.50
Purchase #7	$174.63	12.550%	$196.5461	$196.55	$196.55	$196.50
7 purchase totals =	$1,032.99		$1,109.9110	$1,109.92	$1,109.90	$1,109.90