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	$100.70	10.450%	$111.2232	$111.22	$111.20	$111.20
Purchase #2	$224.99	12.860%	$253.9237	$253.92	$253.90	$253.90
Purchase #3	$123.44	4.616%	$129.138	$129.14	$129.15	$129.10
Purchase #4	$221.95	9.605%	$243.2683	$243.27	$243.25	$243.30
Purchase #5	$46.75	12.517%	$52.6017	$52.60	$52.60	$52.60
Purchase #6	$52.82	11.741%	$59.0216	$59.02	$59.00	$59.00
Purchase #7	$64.80	10.447%	$71.5697	$71.57	$71.55	$71.60
7 purchase totals =	$835.45		$920.7462	$920.74	$920.65	$920.70