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	$207.84	12.300%	$233.4043	$233.40	$233.40	$233.40
Purchase #2	$116.54	12.715%	$131.3581	$131.36	$131.35	$131.40
Purchase #3	$224.96	5.715%	$237.8165	$237.82	$237.80	$237.80
Purchase #4	$179.88	6.181%	$190.9984	$191.00	$191.00	$191.00
Purchase #5	$93.27	11.253%	$103.7657	$103.77	$103.75	$103.80
Purchase #6	$56.56	9.715%	$62.0548	$62.05	$62.05	$62.10
Purchase #7	$161.64	12.846%	$182.4043	$182.40	$182.40	$182.40
7 purchase totals =	$1,040.69		$1,141.8021	$1,141.80	$1,141.75	$1,141.90