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	$204.57	13.702%	$232.6002	$232.60	$232.60	$232.60
Purchase #2	$201.45	3.199%	$207.8944	$207.89	$207.90	$207.90
Purchase #3	$157.42	8.793%	$171.2619	$171.26	$171.25	$171.30
Purchase #4	$51.65	4.333%	$53.888	$53.89	$53.90	$53.90
Purchase #5	$159.91	3.473%	$165.4637	$165.46	$165.45	$165.50
Purchase #6	$64.88	11.749%	$72.5028	$72.50	$72.50	$72.50
Purchase #7	$169.31	4.128%	$176.2991	$176.30	$176.30	$176.30
7 purchase totals =	$1,009.19		$1,079.9101	$1,079.90	$1,079.90	$1,080.00