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	$219.29	11.598%	$244.7233	$244.72	$244.70	$244.70
Purchase #2	$101.92	7.752%	$109.8208	$109.82	$109.80	$109.80
Purchase #3	$23.40	12.538%	$26.3339	$26.33	$26.35	$26.30
Purchase #4	$80.96	11.504%	$90.2736	$90.27	$90.25	$90.30
Purchase #5	$99.85	3.181%	$103.0262	$103.03	$103.05	$103.00
Purchase #6	$107.78	11.835%	$120.5358	$120.54	$120.55	$120.50
Purchase #7	$57.33	11.488%	$63.9161	$63.92	$63.90	$63.90
7 purchase totals =	$690.53		$758.6297	$758.63	$758.60	$758.50