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	$162.86	12.301%	$182.8934	$182.89	$182.90	$182.90
Purchase #2	$119.52	9.229%	$130.5505	$130.55	$130.55	$130.60
Purchase #3	$154.67	8.790%	$168.2655	$168.27	$168.25	$168.30
Purchase #4	$112.34	5.504%	$118.5232	$118.52	$118.50	$118.50
Purchase #5	$143.64	3.582%	$148.7852	$148.79	$148.80	$148.80
Purchase #6	$115.82	13.376%	$131.3121	$131.31	$131.30	$131.30
Purchase #7	$95.97	10.705%	$106.2436	$106.24	$106.25	$106.20
7 purchase totals =	$904.82		$986.5735	$986.57	$986.55	$986.60