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	$168.94	11.492%	$188.3546	$188.35	$188.35	$188.40
Purchase #2	$187.75	11.226%	$208.8268	$208.83	$208.85	$208.80
Purchase #3	$20.75	11.145%	$23.0626	$23.06	$23.05	$23.10
Purchase #4	$215.29	13.487%	$244.3262	$244.33	$244.35	$244.30
Purchase #5	$102.44	7.273%	$109.8905	$109.89	$109.90	$109.90
Purchase #6	$234.78	12.183%	$263.3832	$263.38	$263.40	$263.40
Purchase #7	$62.84	4.665%	$65.7715	$65.77	$65.75	$65.80
7 purchase totals =	$992.79		$1,103.6154	$1,103.61	$1,103.65	$1,103.70