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	$52.83	3.260%	$54.5523	$54.55	$54.55	$54.60
Purchase #2	$249.38	13.204%	$282.3081	$282.31	$282.30	$282.30
Purchase #3	$83.55	3.293%	$86.3013	$86.30	$86.30	$86.30
Purchase #4	$30.33	3.691%	$31.4495	$31.45	$31.45	$31.40
Purchase #5	$218.63	12.291%	$245.5018	$245.50	$245.50	$245.50
Purchase #6	$121.88	4.664%	$127.5645	$127.56	$127.55	$127.60
Purchase #7	$182.61	13.371%	$207.0268	$207.03	$207.05	$207.00
7 purchase totals =	$939.21		$1,034.7043	$1,034.70	$1,034.70	$1,034.70