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	$83.53	4.398%	$87.2036	$87.20	$87.20	$87.20
Purchase #2	$27.52	3.452%	$28.47	$28.47	$28.45	$28.50
Purchase #3	$174.33	9.804%	$191.4213	$191.42	$191.40	$191.40
Purchase #4	$192.93	6.549%	$205.565	$205.57	$205.55	$205.60
Purchase #5	$69.63	9.768%	$76.4315	$76.43	$76.45	$76.40
Purchase #6	$216.66	7.700%	$233.3428	$233.34	$233.35	$233.30
Purchase #7	$164.55	10.682%	$182.1272	$182.13	$182.15	$182.10
7 purchase totals =	$929.15		$1,004.5614	$1,004.56	$1,004.55	$1,004.50