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	$26.43	4.780%	$27.6934	$27.69	$27.70	$27.70
Purchase #2	$245.78	7.572%	$264.3905	$264.39	$264.40	$264.40
Purchase #3	$113.46	4.596%	$118.6746	$118.67	$118.65	$118.70
Purchase #4	$174.83	4.323%	$182.3879	$182.39	$182.40	$182.40
Purchase #5	$239.97	5.598%	$253.4035	$253.40	$253.40	$253.40
Purchase #6	$20.78	6.660%	$22.1639	$22.16	$22.15	$22.20
Purchase #7	$208.44	3.429%	$215.5874	$215.59	$215.60	$215.60
7 purchase totals =	$1,029.69		$1,084.3012	$1,084.29	$1,084.30	$1,084.40