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	$152.61	3.761%	$158.3497	$158.35	$158.35	$158.30
Purchase #2	$248.84	5.574%	$262.7103	$262.71	$262.70	$262.70
Purchase #3	$112.27	6.502%	$119.5698	$119.57	$119.55	$119.60
Purchase #4	$196.33	3.516%	$203.233	$203.23	$203.25	$203.20
Purchase #5	$26.52	4.871%	$27.8118	$27.81	$27.80	$27.80
Purchase #6	$64.37	12.740%	$72.5707	$72.57	$72.55	$72.60
Purchase #7	$237.33	11.713%	$265.1285	$265.13	$265.15	$265.10
7 purchase totals =	$1,038.27		$1,109.3738	$1,109.37	$1,109.35	$1,109.30