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	$52.56	12.809%	$59.2924	$59.29	$59.30	$59.30
Purchase #2	$151.27	4.730%	$158.4251	$158.43	$158.45	$158.40
Purchase #3	$177.93	11.419%	$198.2478	$198.25	$198.25	$198.20
Purchase #4	$235.78	9.744%	$258.7544	$258.75	$258.75	$258.80
Purchase #5	$117.65	11.457%	$131.1292	$131.13	$131.15	$131.10
Purchase #6	$191.48	11.746%	$213.9712	$213.97	$213.95	$214.00
Purchase #7	$138.77	12.219%	$155.7263	$155.73	$155.75	$155.70
7 purchase totals =	$1,065.44		$1,175.5464	$1,175.55	$1,175.60	$1,175.50