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	$102.53	12.873%	$115.7287	$115.73	$115.75	$115.70
Purchase #2	$196.50	11.193%	$218.4942	$218.49	$218.50	$218.50
Purchase #3	$123.30	4.135%	$128.3985	$128.40	$128.40	$128.40
Purchase #4	$61.98	9.145%	$67.6481	$67.65	$67.65	$67.60
Purchase #5	$133.92	13.863%	$152.4853	$152.49	$152.50	$152.50
Purchase #6	$250.69	11.542%	$279.6246	$279.62	$279.60	$279.60
Purchase #7	$159.52	5.744%	$168.6828	$168.68	$168.70	$168.70
7 purchase totals =	$1,028.44		$1,131.0622	$1,131.06	$1,131.10	$1,131.00