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	$208.90	11.736%	$233.4165	$233.42	$233.40	$233.40
Purchase #2	$214.35	10.667%	$237.2147	$237.21	$237.20	$237.20
Purchase #3	$58.67	12.193%	$65.8236	$65.82	$65.80	$65.80
Purchase #4	$99.97	11.547%	$111.5135	$111.51	$111.50	$111.50
Purchase #5	$141.38	9.447%	$154.7362	$154.74	$154.75	$154.70
Purchase #6	$23.37	11.672%	$26.0977	$26.10	$26.10	$26.10
Purchase #7	$179.56	4.282%	$187.2488	$187.25	$187.25	$187.20
7 purchase totals =	$926.20		$1,016.0510	$1,016.05	$1,016.00	$1,015.90