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	$72.93	13.166%	$82.532	$82.53	$82.55	$82.50
Purchase #2	$41.36	3.806%	$42.9342	$42.93	$42.95	$42.90
Purchase #3	$10.84	13.553%	$12.3091	$12.31	$12.30	$12.30
Purchase #4	$205.73	12.749%	$231.9585	$231.96	$231.95	$232.00
Purchase #5	$85.46	7.601%	$91.9558	$91.96	$91.95	$92.00
Purchase #6	$89.58	10.171%	$98.6912	$98.69	$98.70	$98.70
Purchase #7	$249.39	5.238%	$262.453	$262.45	$262.45	$262.50
7 purchase totals =	$755.29		$822.8338	$822.83	$822.85	$822.90