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	$250.65	10.872%	$277.9007	$277.90	$277.90	$277.90
Purchase #2	$193.72	13.104%	$219.1051	$219.11	$219.10	$219.10
Purchase #3	$79.96	13.362%	$90.6443	$90.64	$90.65	$90.60
Purchase #4	$29.37	3.737%	$30.4676	$30.47	$30.45	$30.50
Purchase #5	$62.80	7.149%	$67.2896	$67.29	$67.30	$67.30
Purchase #6	$211.60	3.393%	$218.7796	$218.78	$218.80	$218.80
Purchase #7	$107.86	11.798%	$120.5853	$120.59	$120.60	$120.60
7 purchase totals =	$935.96		$1,024.7722	$1,024.78	$1,024.80	$1,024.80