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	$218.70	8.800%	$237.9456	$237.95	$237.95	$237.90
Purchase #2	$185.55	6.109%	$196.8852	$196.89	$196.90	$196.90
Purchase #3	$111.82	7.239%	$119.9146	$119.91	$119.90	$119.90
Purchase #4	$82.38	7.239%	$88.3435	$88.34	$88.35	$88.30
Purchase #5	$185.59	8.471%	$201.3113	$201.31	$201.30	$201.30
Purchase #6	$100.65	10.645%	$111.3642	$111.36	$111.35	$111.40
Purchase #7	$104.68	3.727%	$108.5814	$108.58	$108.60	$108.60
7 purchase totals =	$989.37		$1,064.3458	$1,064.34	$1,064.35	$1,064.30