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	$222.92	6.359%	$237.0955	$237.10	$237.10	$237.10
Purchase #2	$117.52	12.331%	$132.0114	$132.01	$132.00	$132.00
Purchase #3	$25.38	11.596%	$28.3231	$28.32	$28.30	$28.30
Purchase #4	$116.99	12.754%	$131.9109	$131.91	$131.90	$131.90
Purchase #5	$7.26	3.596%	$7.5211	$7.52	$7.50	$7.50
Purchase #6	$38.67	10.243%	$42.631	$42.63	$42.65	$42.60
Purchase #7	$215.51	13.477%	$244.5543	$244.55	$244.55	$244.60
7 purchase totals =	$744.25		$824.0473	$824.04	$824.00	$824.00