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	$96.49	9.564%	$105.7183	$105.72	$105.70	$105.70
Purchase #2	$129.26	6.609%	$137.8028	$137.80	$137.80	$137.80
Purchase #3	$46.79	8.709%	$50.8649	$50.86	$50.85	$50.90
Purchase #4	$118.55	7.672%	$127.6452	$127.65	$127.65	$127.60
Purchase #5	$250.46	12.185%	$280.9786	$280.98	$281.00	$281.00
Purchase #6	$171.77	12.108%	$192.5679	$192.57	$192.55	$192.60
Purchase #7	$105.32	12.244%	$118.2154	$118.22	$118.20	$118.20
7 purchase totals =	$918.64		$1,013.7931	$1,013.80	$1,013.75	$1,013.80