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	$187.77	13.367%	$212.8692	$212.87	$212.85	$212.90
Purchase #2	$231.52	12.103%	$259.5409	$259.54	$259.55	$259.50
Purchase #3	$160.90	8.318%	$174.2837	$174.28	$174.30	$174.30
Purchase #4	$49.70	12.279%	$55.8027	$55.80	$55.80	$55.80
Purchase #5	$109.45	9.558%	$119.9112	$119.91	$119.90	$119.90
Purchase #6	$41.35	3.471%	$42.7853	$42.79	$42.80	$42.80
Purchase #7	$63.81	12.601%	$71.8507	$71.85	$71.85	$71.90
7 purchase totals =	$844.50		$937.0437	$937.04	$937.05	$937.10