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	$98.34	3.234%	$101.5203	$101.52	$101.50	$101.50
Purchase #2	$34.87	10.293%	$38.4592	$38.46	$38.45	$38.50
Purchase #3	$204.79	4.445%	$213.8929	$213.89	$213.90	$213.90
Purchase #4	$197.91	3.806%	$205.4425	$205.44	$205.45	$205.40
Purchase #5	$160.45	10.200%	$176.8159	$176.82	$176.80	$176.80
Purchase #6	$162.31	11.340%	$180.716	$180.72	$180.70	$180.70
Purchase #7	$175.88	11.667%	$196.3999	$196.40	$196.40	$196.40
7 purchase totals =	$1,034.55		$1,113.2467	$1,113.25	$1,113.20	$1,113.20