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	$143.93	9.149%	$157.0982	$157.10	$157.10	$157.10
Purchase #2	$155.56	12.725%	$175.355	$175.36	$175.35	$175.40
Purchase #3	$89.75	6.380%	$95.4761	$95.48	$95.50	$95.50
Purchase #4	$224.99	3.754%	$233.4361	$233.44	$233.45	$233.40
Purchase #5	$163.76	12.422%	$184.1023	$184.10	$184.10	$184.10
Purchase #6	$203.49	9.557%	$222.9375	$222.94	$222.95	$222.90
Purchase #7	$70.61	11.484%	$78.7189	$78.72	$78.70	$78.70
7 purchase totals =	$1,052.09		$1,147.1241	$1,147.14	$1,147.15	$1,147.10