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	$115.69	12.814%	$130.5145	$130.51	$130.50	$130.50
Purchase #2	$14.94	3.493%	$15.4619	$15.46	$15.45	$15.50
Purchase #3	$106.57	10.682%	$117.9538	$117.95	$117.95	$118.00
Purchase #4	$111.82	6.342%	$118.9116	$118.91	$118.90	$118.90
Purchase #5	$32.61	13.403%	$36.9807	$36.98	$37.00	$37.00
Purchase #6	$141.91	3.545%	$146.9407	$146.94	$146.95	$146.90
Purchase #7	$204.69	5.832%	$216.6275	$216.63	$216.65	$216.60
7 purchase totals =	$728.23		$783.3907	$783.38	$783.40	$783.40