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	$190.53	12.769%	$214.8588	$214.86	$214.85	$214.90
Purchase #2	$172.52	6.513%	$183.7562	$183.76	$183.75	$183.80
Purchase #3	$26.73	6.835%	$28.557	$28.56	$28.55	$28.60
Purchase #4	$168.93	5.629%	$178.4391	$178.44	$178.45	$178.40
Purchase #5	$235.34	3.181%	$242.8262	$242.83	$242.85	$242.80
Purchase #6	$64.37	4.584%	$67.3207	$67.32	$67.30	$67.30
Purchase #7	$152.51	8.166%	$164.964	$164.96	$164.95	$165.00
7 purchase totals =	$1,010.93		$1,080.7220	$1,080.73	$1,080.70	$1,080.80