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	$136.49	11.528%	$152.2246	$152.22	$152.20	$152.20
Purchase #2	$101.93	9.624%	$111.7397	$111.74	$111.75	$111.70
Purchase #3	$196.80	12.361%	$221.1264	$221.13	$221.15	$221.10
Purchase #4	$71.97	9.354%	$78.7021	$78.70	$78.70	$78.70
Purchase #5	$220.39	9.221%	$240.7122	$240.71	$240.70	$240.70
Purchase #6	$58.81	7.768%	$63.3784	$63.38	$63.40	$63.40
Purchase #7	$144.37	6.841%	$154.2464	$154.25	$154.25	$154.20
7 purchase totals =	$930.76		$1,022.1298	$1,022.13	$1,022.15	$1,022.00