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	$173.51	9.439%	$189.8876	$189.89	$189.90	$189.90
Purchase #2	$66.59	8.103%	$71.9858	$71.99	$72.00	$72.00
Purchase #3	$101.41	12.329%	$113.9128	$113.91	$113.90	$113.90
Purchase #4	$81.86	8.804%	$89.067	$89.07	$89.05	$89.10
Purchase #5	$66.32	11.176%	$73.7319	$73.73	$73.75	$73.70
Purchase #6	$233.89	3.215%	$241.4096	$241.41	$241.40	$241.40
Purchase #7	$238.43	4.710%	$249.6601	$249.66	$249.65	$249.70
7 purchase totals =	$962.01		$1,029.6548	$1,029.66	$1,029.65	$1,029.70