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	$198.42	9.680%	$217.6271	$217.63	$217.65	$217.60
Purchase #2	$114.25	12.851%	$128.9323	$128.93	$128.95	$128.90
Purchase #3	$151.35	4.468%	$158.1123	$158.11	$158.10	$158.10
Purchase #4	$106.43	5.515%	$112.2996	$112.30	$112.30	$112.30
Purchase #5	$59.87	7.725%	$64.495	$64.50	$64.50	$64.50
Purchase #6	$133.83	10.398%	$147.7456	$147.75	$147.75	$147.70
Purchase #7	$137.56	10.527%	$152.0409	$152.04	$152.05	$152.00
7 purchase totals =	$901.71		$981.2528	$981.26	$981.30	$981.10