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	$84.80	13.264%	$96.0479	$96.05	$96.05	$96.00
Purchase #2	$129.86	8.225%	$140.541	$140.54	$140.55	$140.50
Purchase #3	$156.55	6.362%	$166.5097	$166.51	$166.50	$166.50
Purchase #4	$208.59	6.166%	$221.4517	$221.45	$221.45	$221.50
Purchase #5	$91.71	5.758%	$96.9907	$96.99	$97.00	$97.00
Purchase #6	$211.67	6.182%	$224.7554	$224.76	$224.75	$224.80
Purchase #7	$64.41	12.744%	$72.6184	$72.62	$72.60	$72.60
7 purchase totals =	$947.59		$1,018.9148	$1,018.92	$1,018.90	$1,018.90