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	$162.75	6.744%	$173.7259	$173.73	$173.75	$173.70
Purchase #2	$218.34	13.780%	$248.4273	$248.43	$248.45	$248.40
Purchase #3	$60.78	5.168%	$63.9211	$63.92	$63.90	$63.90
Purchase #4	$112.61	9.524%	$123.335	$123.34	$123.35	$123.30
Purchase #5	$68.98	13.105%	$78.0198	$78.02	$78.00	$78.00
Purchase #6	$98.55	11.505%	$109.8882	$109.89	$109.90	$109.90
Purchase #7	$186.38	5.512%	$196.6533	$196.65	$196.65	$196.70
7 purchase totals =	$908.39		$993.9706	$993.98	$994.00	$993.90