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	$225.47	7.275%	$241.8729	$241.87	$241.85	$241.90
Purchase #2	$114.82	10.814%	$127.2366	$127.24	$127.25	$127.20
Purchase #3	$30.78	7.409%	$33.0605	$33.06	$33.05	$33.10
Purchase #4	$53.83	4.558%	$56.2836	$56.28	$56.30	$56.30
Purchase #5	$174.43	5.241%	$183.5719	$183.57	$183.55	$183.60
Purchase #6	$90.90	11.645%	$101.4853	$101.49	$101.50	$101.50
Purchase #7	$231.84	8.459%	$251.4513	$251.45	$251.45	$251.50
7 purchase totals =	$922.07		$994.9621	$994.96	$994.95	$995.10