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	$165.64	3.854%	$172.0238	$172.02	$172.00	$172.00
Purchase #2	$98.28	13.646%	$111.6913	$111.69	$111.70	$111.70
Purchase #3	$210.75	4.514%	$220.2633	$220.26	$220.25	$220.30
Purchase #4	$144.30	13.547%	$163.8483	$163.85	$163.85	$163.80
Purchase #5	$191.55	12.722%	$215.919	$215.92	$215.90	$215.90
Purchase #6	$142.61	9.235%	$155.78	$155.78	$155.80	$155.80
Purchase #7	$68.28	6.261%	$72.555	$72.56	$72.55	$72.60
7 purchase totals =	$1,021.41		$1,112.0807	$1,112.08	$1,112.05	$1,112.10