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	$89.96	4.789%	$94.2682	$94.27	$94.25	$94.30
Purchase #2	$232.96	5.667%	$246.1618	$246.16	$246.15	$246.20
Purchase #3	$90.79	13.799%	$103.3181	$103.32	$103.30	$103.30
Purchase #4	$176.54	13.531%	$200.4276	$200.43	$200.45	$200.40
Purchase #5	$72.96	4.841%	$76.492	$76.49	$76.50	$76.50
Purchase #6	$196.50	10.567%	$217.2642	$217.26	$217.25	$217.30
Purchase #7	$72.91	13.482%	$82.7397	$82.74	$82.75	$82.70
7 purchase totals =	$932.62		$1,020.6716	$1,020.67	$1,020.65	$1,020.70