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	$117.51	3.758%	$121.926	$121.93	$121.95	$121.90
Purchase #2	$197.45	12.527%	$222.1846	$222.18	$222.20	$222.20
Purchase #3	$231.44	4.537%	$241.9404	$241.94	$241.95	$241.90
Purchase #4	$64.81	4.314%	$67.6059	$67.61	$67.60	$67.60
Purchase #5	$21.67	5.840%	$22.9355	$22.94	$22.95	$22.90
Purchase #6	$79.75	3.368%	$82.436	$82.44	$82.45	$82.40
Purchase #7	$218.48	11.271%	$243.1049	$243.10	$243.10	$243.10
7 purchase totals =	$931.11		$1,002.1333	$1,002.14	$1,002.20	$1,002.00