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	$166.46	3.258%	$171.8833	$171.88	$171.90	$171.90
Purchase #2	$141.63	3.549%	$146.6564	$146.66	$146.65	$146.70
Purchase #3	$62.79	9.210%	$68.573	$68.57	$68.55	$68.60
Purchase #4	$242.45	4.614%	$253.6366	$253.64	$253.65	$253.60
Purchase #5	$213.70	5.430%	$225.3039	$225.30	$225.30	$225.30
Purchase #6	$82.74	9.387%	$90.5068	$90.51	$90.50	$90.50
Purchase #7	$78.86	12.316%	$88.5724	$88.57	$88.55	$88.60
7 purchase totals =	$988.63		$1,045.1324	$1,045.13	$1,045.10	$1,045.20