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	$78.45	6.460%	$83.5179	$83.52	$83.50	$83.50
Purchase #2	$140.58	8.232%	$152.1525	$152.15	$152.15	$152.20
Purchase #3	$42.42	4.280%	$44.2356	$44.24	$44.25	$44.20
Purchase #4	$174.69	6.737%	$186.4589	$186.46	$186.45	$186.50
Purchase #5	$190.83	6.651%	$203.5221	$203.52	$203.50	$203.50
Purchase #6	$184.68	6.508%	$196.699	$196.70	$196.70	$196.70
Purchase #7	$155.51	13.392%	$176.3359	$176.34	$176.35	$176.30
7 purchase totals =	$967.16		$1,042.9219	$1,042.93	$1,042.90	$1,042.90