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	$166.72	3.550%	$172.6386	$172.64	$172.65	$172.60
Purchase #2	$148.36	12.642%	$167.1157	$167.12	$167.10	$167.10
Purchase #3	$137.26	4.498%	$143.434	$143.43	$143.45	$143.40
Purchase #4	$224.88	6.261%	$238.9597	$238.96	$238.95	$239.00
Purchase #5	$43.64	6.872%	$46.6389	$46.64	$46.65	$46.60
Purchase #6	$58.72	8.438%	$63.6748	$63.67	$63.65	$63.70
Purchase #7	$168.96	6.858%	$180.5473	$180.55	$180.55	$180.50
7 purchase totals =	$948.54		$1,013.0090	$1,013.01	$1,013.00	$1,012.90