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	$121.46	4.686%	$127.1516	$127.15	$127.15	$127.20
Purchase #2	$184.30	7.506%	$198.1336	$198.13	$198.15	$198.10
Purchase #3	$233.36	6.417%	$248.3347	$248.33	$248.35	$248.30
Purchase #4	$90.33	3.481%	$93.4744	$93.47	$93.45	$93.50
Purchase #5	$59.55	5.202%	$62.6478	$62.65	$62.65	$62.60
Purchase #6	$67.27	12.131%	$75.4305	$75.43	$75.45	$75.40
Purchase #7	$205.77	13.290%	$233.1168	$233.12	$233.10	$233.10
7 purchase totals =	$962.04		$1,038.2894	$1,038.28	$1,038.30	$1,038.20