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	$179.37	3.398%	$185.465	$185.47	$185.45	$185.50
Purchase #2	$166.53	8.417%	$180.5468	$180.55	$180.55	$180.50
Purchase #3	$233.44	7.461%	$250.857	$250.86	$250.85	$250.90
Purchase #4	$17.65	12.439%	$19.8455	$19.85	$19.85	$19.80
Purchase #5	$237.51	6.872%	$253.8317	$253.83	$253.85	$253.80
Purchase #6	$19.26	13.807%	$21.9192	$21.92	$21.90	$21.90
Purchase #7	$241.42	12.641%	$271.9379	$271.94	$271.95	$271.90
7 purchase totals =	$1,095.18		$1,184.4031	$1,184.42	$1,184.40	$1,184.30