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	$160.91	9.327%	$175.9181	$175.92	$175.90	$175.90
Purchase #2	$15.40	9.315%	$16.8345	$16.83	$16.85	$16.80
Purchase #3	$68.68	5.389%	$72.3812	$72.38	$72.40	$72.40
Purchase #4	$41.54	7.779%	$44.7714	$44.77	$44.75	$44.80
Purchase #5	$185.99	5.653%	$196.504	$196.50	$196.50	$196.50
Purchase #6	$93.83	4.524%	$98.0749	$98.07	$98.05	$98.10
Purchase #7	$143.86	6.248%	$152.8484	$152.85	$152.85	$152.80
7 purchase totals =	$710.21		$757.3325	$757.32	$757.30	$757.30