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	$79.40	13.815%	$90.3691	$90.37	$90.35	$90.40
Purchase #2	$109.43	12.677%	$123.3024	$123.30	$123.30	$123.30
Purchase #3	$203.39	6.162%	$215.9229	$215.92	$215.90	$215.90
Purchase #4	$101.95	10.264%	$112.4141	$112.41	$112.40	$112.40
Purchase #5	$214.50	5.227%	$225.7119	$225.71	$225.70	$225.70
Purchase #6	$221.67	7.310%	$237.8741	$237.87	$237.85	$237.90
Purchase #7	$115.84	8.621%	$125.8266	$125.83	$125.85	$125.80
7 purchase totals =	$1,046.18		$1,131.4211	$1,131.41	$1,131.35	$1,131.40