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	$231.27	11.587%	$258.0673	$258.07	$258.05	$258.10
Purchase #2	$133.51	6.424%	$142.0867	$142.09	$142.10	$142.10
Purchase #3	$107.57	3.271%	$111.0886	$111.09	$111.10	$111.10
Purchase #4	$193.90	9.221%	$211.7795	$211.78	$211.80	$211.80
Purchase #5	$70.57	9.615%	$77.3553	$77.36	$77.35	$77.40
Purchase #6	$132.85	7.610%	$142.9599	$142.96	$142.95	$143.00
Purchase #7	$90.60	9.407%	$99.1227	$99.12	$99.10	$99.10
7 purchase totals =	$960.27		$1,042.4600	$1,042.47	$1,042.45	$1,042.60