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	$78.36	4.762%	$82.0915	$82.09	$82.10	$82.10
Purchase #2	$79.95	4.243%	$83.3423	$83.34	$83.35	$83.30
Purchase #3	$52.55	7.835%	$56.6673	$56.67	$56.65	$56.70
Purchase #4	$45.52	5.750%	$48.1374	$48.14	$48.15	$48.10
Purchase #5	$121.27	3.456%	$125.4611	$125.46	$125.45	$125.50
Purchase #6	$214.39	5.539%	$226.2651	$226.27	$226.25	$226.30
Purchase #7	$54.76	8.786%	$59.5712	$59.57	$59.55	$59.60
7 purchase totals =	$646.80		$681.5359	$681.54	$681.50	$681.60