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	$40.63	12.802%	$45.8315	$45.83	$45.85	$45.80
Purchase #2	$230.52	5.295%	$242.726	$242.73	$242.75	$242.70
Purchase #3	$75.84	8.356%	$82.1772	$82.18	$82.20	$82.20
Purchase #4	$167.61	4.471%	$175.1038	$175.10	$175.10	$175.10
Purchase #5	$109.87	7.813%	$118.4541	$118.45	$118.45	$118.50
Purchase #6	$120.53	9.409%	$131.8707	$131.87	$131.85	$131.90
Purchase #7	$191.25	12.685%	$215.5101	$215.51	$215.50	$215.50
7 purchase totals =	$936.25		$1,011.6734	$1,011.67	$1,011.70	$1,011.70