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	$125.54	4.738%	$131.4881	$131.49	$131.50	$131.50
Purchase #2	$25.39	8.279%	$27.492	$27.49	$27.50	$27.50
Purchase #3	$199.98	11.232%	$222.4418	$222.44	$222.45	$222.40
Purchase #4	$34.71	3.697%	$35.9932	$35.99	$36.00	$36.00
Purchase #5	$48.83	9.479%	$53.4586	$53.46	$53.45	$53.50
Purchase #6	$178.65	11.294%	$198.8267	$198.83	$198.85	$198.80
Purchase #7	$162.45	3.178%	$167.6127	$167.61	$167.60	$167.60
7 purchase totals =	$775.55		$837.3131	$837.31	$837.35	$837.30