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	$71.72	7.490%	$77.0918	$77.09	$77.10	$77.10
Purchase #2	$185.85	13.607%	$211.1386	$211.14	$211.15	$211.10
Purchase #3	$177.47	5.874%	$187.8946	$187.89	$187.90	$187.90
Purchase #4	$55.63	6.289%	$59.1286	$59.13	$59.15	$59.10
Purchase #5	$137.71	9.436%	$150.7043	$150.70	$150.70	$150.70
Purchase #6	$224.81	3.731%	$233.1977	$233.20	$233.20	$233.20
Purchase #7	$160.75	13.531%	$182.5011	$182.50	$182.50	$182.50
7 purchase totals =	$1,013.94		$1,101.6567	$1,101.65	$1,101.70	$1,101.60