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	$121.51	8.166%	$131.4325	$131.43	$131.45	$131.40
Purchase #2	$225.61	12.452%	$253.703	$253.70	$253.70	$253.70
Purchase #3	$53.28	11.467%	$59.3896	$59.39	$59.40	$59.40
Purchase #4	$104.75	12.724%	$118.0784	$118.08	$118.10	$118.10
Purchase #5	$153.79	6.712%	$164.1124	$164.11	$164.10	$164.10
Purchase #6	$191.42	4.748%	$200.5086	$200.51	$200.50	$200.50
Purchase #7	$13.74	5.713%	$14.525	$14.53	$14.55	$14.50
7 purchase totals =	$864.10		$941.7495	$941.75	$941.80	$941.70