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	$148.96	5.149%	$156.63	$156.63	$156.65	$156.60
Purchase #2	$250.81	5.753%	$265.2391	$265.24	$265.25	$265.20
Purchase #3	$124.49	11.783%	$139.1587	$139.16	$139.15	$139.20
Purchase #4	$63.81	4.366%	$66.5959	$66.60	$66.60	$66.60
Purchase #5	$43.35	4.637%	$45.3601	$45.36	$45.35	$45.40
Purchase #6	$78.58	5.419%	$82.8383	$82.84	$82.85	$82.80
Purchase #7	$171.65	4.172%	$178.8112	$178.81	$178.80	$178.80
7 purchase totals =	$881.65		$934.6333	$934.64	$934.65	$934.60