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	$41.48	6.242%	$44.0692	$44.07	$44.05	$44.10
Purchase #2	$114.40	8.319%	$123.9169	$123.92	$123.90	$123.90
Purchase #3	$101.27	9.726%	$111.1195	$111.12	$111.10	$111.10
Purchase #4	$175.56	6.533%	$187.0293	$187.03	$187.05	$187.00
Purchase #5	$118.78	9.597%	$130.1793	$130.18	$130.20	$130.20
Purchase #6	$135.38	5.511%	$142.8408	$142.84	$142.85	$142.80
Purchase #7	$137.66	6.424%	$146.5033	$146.50	$146.50	$146.50
7 purchase totals =	$824.53		$885.6583	$885.66	$885.65	$885.60