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	$115.80	13.859%	$131.8487	$131.85	$131.85	$131.80
Purchase #2	$149.36	4.746%	$156.4486	$156.45	$156.45	$156.40
Purchase #3	$82.39	13.508%	$93.5192	$93.52	$93.50	$93.50
Purchase #4	$67.75	4.769%	$70.981	$70.98	$71.00	$71.00
Purchase #5	$68.54	12.790%	$77.3063	$77.31	$77.30	$77.30
Purchase #6	$57.51	7.782%	$61.9854	$61.99	$62.00	$62.00
Purchase #7	$184.56	3.203%	$190.4715	$190.47	$190.45	$190.50
7 purchase totals =	$725.91		$782.5607	$782.57	$782.55	$782.50