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	$196.79	9.310%	$215.1111	$215.11	$215.10	$215.10
Purchase #2	$82.28	9.500%	$90.0966	$90.10	$90.10	$90.10
Purchase #3	$213.54	10.411%	$235.7716	$235.77	$235.75	$235.80
Purchase #4	$133.50	6.258%	$141.8544	$141.85	$141.85	$141.90
Purchase #5	$122.31	11.614%	$136.5151	$136.52	$136.50	$136.50
Purchase #6	$171.64	4.618%	$179.5663	$179.57	$179.55	$179.60
Purchase #7	$168.97	8.757%	$183.7667	$183.77	$183.75	$183.80
7 purchase totals =	$1,089.03		$1,182.6818	$1,182.69	$1,182.60	$1,182.80