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	$89.67	3.460%	$92.7726	$92.77	$92.75	$92.80
Purchase #2	$95.47	13.464%	$108.3241	$108.32	$108.30	$108.30
Purchase #3	$233.85	4.631%	$244.6796	$244.68	$244.70	$244.70
Purchase #4	$16.67	10.712%	$18.4557	$18.46	$18.45	$18.50
Purchase #5	$119.46	10.364%	$131.8408	$131.84	$131.85	$131.80
Purchase #6	$62.86	11.607%	$70.1562	$70.16	$70.15	$70.20
Purchase #7	$171.45	13.556%	$194.6918	$194.69	$194.70	$194.70
7 purchase totals =	$789.43		$860.9208	$860.92	$860.90	$861.00