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	$76.65	7.690%	$82.5444	$82.54	$82.55	$82.50
Purchase #2	$26.41	9.651%	$28.9588	$28.96	$28.95	$29.00
Purchase #3	$40.34	8.575%	$43.7992	$43.80	$43.80	$43.80
Purchase #4	$13.32	8.190%	$14.4109	$14.41	$14.40	$14.40
Purchase #5	$210.92	6.867%	$225.4039	$225.40	$225.40	$225.40
Purchase #6	$240.94	4.385%	$251.5052	$251.51	$251.50	$251.50
Purchase #7	$123.28	11.484%	$137.4375	$137.44	$137.45	$137.40
7 purchase totals =	$731.86		$784.0599	$784.06	$784.05	$784.00