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	$45.70	7.557%	$49.1535	$49.15	$49.15	$49.20
Purchase #2	$85.50	6.514%	$91.0695	$91.07	$91.05	$91.10
Purchase #3	$226.53	13.404%	$256.8941	$256.89	$256.90	$256.90
Purchase #4	$154.84	6.139%	$164.3456	$164.35	$164.35	$164.30
Purchase #5	$193.35	6.294%	$205.5194	$205.52	$205.50	$205.50
Purchase #6	$43.54	4.444%	$45.4749	$45.47	$45.45	$45.50
Purchase #7	$242.26	5.212%	$254.8866	$254.89	$254.90	$254.90
7 purchase totals =	$991.72		$1,067.3436	$1,067.34	$1,067.30	$1,067.40