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	$206.33	6.661%	$220.0736	$220.07	$220.05	$220.10
Purchase #2	$240.94	11.362%	$268.3156	$268.32	$268.30	$268.30
Purchase #3	$196.30	12.746%	$221.3204	$221.32	$221.30	$221.30
Purchase #4	$126.80	4.644%	$132.6886	$132.69	$132.70	$132.70
Purchase #5	$154.93	12.848%	$174.8354	$174.84	$174.85	$174.80
Purchase #6	$21.77	7.710%	$23.4485	$23.45	$23.45	$23.40
Purchase #7	$18.53	10.566%	$20.4879	$20.49	$20.50	$20.50
7 purchase totals =	$965.60		$1,061.1700	$1,061.18	$1,061.15	$1,061.10