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	$168.69	4.365%	$176.0533	$176.05	$176.05	$176.10
Purchase #2	$245.88	7.326%	$263.8932	$263.89	$263.90	$263.90
Purchase #3	$177.87	4.444%	$185.7745	$185.77	$185.75	$185.80
Purchase #4	$175.95	4.573%	$183.9962	$184.00	$184.00	$184.00
Purchase #5	$140.95	9.709%	$154.6348	$154.63	$154.65	$154.60
Purchase #6	$52.73	4.475%	$55.0897	$55.09	$55.10	$55.10
Purchase #7	$57.98	7.767%	$62.4833	$62.48	$62.50	$62.50
7 purchase totals =	$1,020.05		$1,081.9250	$1,081.91	$1,081.95	$1,082.00