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	$179.89	8.281%	$194.7867	$194.79	$194.80	$194.80
Purchase #2	$72.50	8.866%	$78.9279	$78.93	$78.95	$78.90
Purchase #3	$233.52	9.586%	$255.9052	$255.91	$255.90	$255.90
Purchase #4	$155.92	13.195%	$176.4936	$176.49	$176.50	$176.50
Purchase #5	$130.43	10.432%	$144.0365	$144.04	$144.05	$144.00
Purchase #6	$216.90	5.597%	$229.0399	$229.04	$229.05	$229.00
Purchase #7	$91.48	8.203%	$98.9841	$98.98	$99.00	$99.00
7 purchase totals =	$1,080.64		$1,178.1739	$1,178.18	$1,178.25	$1,178.10