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	$144.39	5.432%	$152.2333	$152.23	$152.25	$152.20
Purchase #2	$248.50	4.866%	$260.592	$260.59	$260.60	$260.60
Purchase #3	$145.46	3.645%	$150.762	$150.76	$150.75	$150.80
Purchase #4	$79.53	13.808%	$90.5115	$90.51	$90.50	$90.50
Purchase #5	$28.75	13.369%	$32.5936	$32.59	$32.60	$32.60
Purchase #6	$233.66	4.677%	$244.5883	$244.59	$244.60	$244.60
Purchase #7	$10.89	5.740%	$11.5151	$11.52	$11.50	$11.50
7 purchase totals =	$891.18		$942.7958	$942.79	$942.80	$942.80