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	$217.60	12.802%	$245.4572	$245.46	$245.45	$245.50
Purchase #2	$56.97	5.536%	$60.1239	$60.12	$60.10	$60.10
Purchase #3	$43.40	11.601%	$48.4348	$48.43	$48.45	$48.40
Purchase #4	$132.76	3.142%	$136.9313	$136.93	$136.95	$136.90
Purchase #5	$227.77	11.318%	$253.549	$253.55	$253.55	$253.50
Purchase #6	$63.64	6.133%	$67.543	$67.54	$67.55	$67.50
Purchase #7	$43.43	4.630%	$45.4408	$45.44	$45.45	$45.40
7 purchase totals =	$785.57		$857.4800	$857.47	$857.50	$857.30