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	$163.96	13.386%	$185.9077	$185.91	$185.90	$185.90
Purchase #2	$248.91	9.804%	$273.3131	$273.31	$273.30	$273.30
Purchase #3	$181.50	8.287%	$196.5409	$196.54	$196.55	$196.50
Purchase #4	$158.56	13.338%	$179.7087	$179.71	$179.70	$179.70
Purchase #5	$48.55	8.824%	$52.8341	$52.83	$52.85	$52.80
Purchase #6	$125.64	4.371%	$131.1317	$131.13	$131.15	$131.10
Purchase #7	$240.31	13.456%	$272.6461	$272.65	$272.65	$272.60
7 purchase totals =	$1,167.43		$1,292.0823	$1,292.08	$1,292.10	$1,291.90