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	$156.85	11.507%	$174.8987	$174.90	$174.90	$174.90
Purchase #2	$19.79	3.434%	$20.4696	$20.47	$20.45	$20.50
Purchase #3	$135.82	5.250%	$142.9506	$142.95	$142.95	$143.00
Purchase #4	$86.46	13.870%	$98.452	$98.45	$98.45	$98.50
Purchase #5	$41.49	11.513%	$46.2667	$46.27	$46.25	$46.30
Purchase #6	$221.86	5.423%	$233.8915	$233.89	$233.90	$233.90
Purchase #7	$221.47	6.694%	$236.2952	$236.30	$236.30	$236.30
7 purchase totals =	$883.74		$953.2243	$953.23	$953.20	$953.40