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	$245.65	8.665%	$266.9356	$266.94	$266.95	$266.90
Purchase #2	$73.56	13.358%	$83.3861	$83.39	$83.40	$83.40
Purchase #3	$169.35	5.741%	$179.0724	$179.07	$179.05	$179.10
Purchase #4	$46.70	7.394%	$50.153	$50.15	$50.15	$50.20
Purchase #5	$50.66	5.155%	$53.2715	$53.27	$53.25	$53.30
Purchase #6	$27.38	13.454%	$31.0637	$31.06	$31.05	$31.10
Purchase #7	$32.46	12.218%	$36.426	$36.43	$36.45	$36.40
7 purchase totals =	$645.76		$700.3083	$700.31	$700.30	$700.40