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	$69.27	11.823%	$77.4598	$77.46	$77.45	$77.50
Purchase #2	$49.56	12.593%	$55.8011	$55.80	$55.80	$55.80
Purchase #3	$116.72	6.507%	$124.315	$124.32	$124.30	$124.30
Purchase #4	$171.59	10.362%	$189.3702	$189.37	$189.35	$189.40
Purchase #5	$137.80	4.403%	$143.8673	$143.87	$143.85	$143.90
Purchase #6	$137.41	10.733%	$152.1582	$152.16	$152.15	$152.20
Purchase #7	$202.97	6.304%	$215.7652	$215.77	$215.75	$215.80
7 purchase totals =	$885.32		$958.7368	$958.75	$958.65	$958.90