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	$148.58	11.149%	$165.1452	$165.15	$165.15	$165.10
Purchase #2	$127.93	7.699%	$137.7793	$137.78	$137.80	$137.80
Purchase #3	$62.71	11.517%	$69.9323	$69.93	$69.95	$69.90
Purchase #4	$183.39	7.212%	$196.6161	$196.62	$196.60	$196.60
Purchase #5	$223.59	3.687%	$231.8338	$231.83	$231.85	$231.80
Purchase #6	$91.32	12.221%	$102.4802	$102.48	$102.50	$102.50
Purchase #7	$153.53	13.219%	$173.8251	$173.83	$173.85	$173.80
7 purchase totals =	$991.05		$1,077.6120	$1,077.62	$1,077.70	$1,077.50