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	$101.80	10.734%	$112.7272	$112.73	$112.75	$112.70
Purchase #2	$36.61	11.596%	$40.8553	$40.86	$40.85	$40.90
Purchase #3	$185.92	12.291%	$208.7714	$208.77	$208.75	$208.80
Purchase #4	$63.26	13.829%	$72.0082	$72.01	$72.00	$72.00
Purchase #5	$145.61	12.653%	$164.034	$164.03	$164.05	$164.00
Purchase #6	$43.65	12.217%	$48.9827	$48.98	$49.00	$49.00
Purchase #7	$155.57	13.765%	$176.9842	$176.98	$177.00	$177.00
7 purchase totals =	$732.42		$824.3630	$824.36	$824.40	$824.40