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	$208.71	9.155%	$227.8174	$227.82	$227.80	$227.80
Purchase #2	$193.28	3.625%	$200.2864	$200.29	$200.30	$200.30
Purchase #3	$153.79	4.403%	$160.5614	$160.56	$160.55	$160.60
Purchase #4	$134.97	12.530%	$151.8817	$151.88	$151.90	$151.90
Purchase #5	$111.40	13.709%	$126.6718	$126.67	$126.65	$126.70
Purchase #6	$113.38	9.242%	$123.8586	$123.86	$123.85	$123.90
Purchase #7	$56.42	4.456%	$58.9341	$58.93	$58.95	$58.90
7 purchase totals =	$971.95		$1,050.0114	$1,050.01	$1,050.00	$1,050.10