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	$212.31	4.199%	$221.2249	$221.22	$221.20	$221.20
Purchase #2	$27.89	5.727%	$29.4873	$29.49	$29.50	$29.50
Purchase #3	$190.96	6.589%	$203.5424	$203.54	$203.55	$203.50
Purchase #4	$46.46	13.199%	$52.5923	$52.59	$52.60	$52.60
Purchase #5	$14.46	11.188%	$16.0778	$16.08	$16.10	$16.10
Purchase #6	$201.42	10.457%	$222.4825	$222.48	$222.50	$222.50
Purchase #7	$143.36	4.846%	$150.3072	$150.31	$150.30	$150.30
7 purchase totals =	$836.86		$895.7144	$895.71	$895.75	$895.70