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	$83.43	12.768%	$94.0823	$94.08	$94.10	$94.10
Purchase #2	$58.30	6.318%	$61.9834	$61.98	$62.00	$62.00
Purchase #3	$122.55	9.746%	$134.4937	$134.49	$134.50	$134.50
Purchase #4	$168.56	8.851%	$183.4792	$183.48	$183.50	$183.50
Purchase #5	$168.46	13.104%	$190.535	$190.54	$190.55	$190.50
Purchase #6	$153.87	6.664%	$164.1239	$164.12	$164.10	$164.10
Purchase #7	$43.27	11.649%	$48.3105	$48.31	$48.30	$48.30
7 purchase totals =	$798.44		$877.0080	$877.00	$877.05	$877.00