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	$86.43	4.354%	$90.1932	$90.19	$90.20	$90.20
Purchase #2	$20.62	10.576%	$22.8008	$22.80	$22.80	$22.80
Purchase #3	$197.25	6.860%	$210.7814	$210.78	$210.80	$210.80
Purchase #4	$131.53	3.589%	$136.2506	$136.25	$136.25	$136.30
Purchase #5	$160.72	13.633%	$182.631	$182.63	$182.65	$182.60
Purchase #6	$177.70	10.465%	$196.2963	$196.30	$196.30	$196.30
Purchase #7	$228.61	5.805%	$241.8808	$241.88	$241.90	$241.90
7 purchase totals =	$1,002.86		$1,080.8341	$1,080.83	$1,080.90	$1,080.90