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	$169.43	13.268%	$191.91	$191.91	$191.90	$191.90
Purchase #2	$224.27	7.537%	$241.1732	$241.17	$241.15	$241.20
Purchase #3	$168.46	7.523%	$181.1332	$181.13	$181.15	$181.10
Purchase #4	$166.84	5.342%	$175.7526	$175.75	$175.75	$175.80
Purchase #5	$205.38	7.161%	$220.0873	$220.09	$220.10	$220.10
Purchase #6	$86.26	7.689%	$92.8925	$92.89	$92.90	$92.90
Purchase #7	$179.48	9.468%	$196.4732	$196.47	$196.45	$196.50
7 purchase totals =	$1,200.12		$1,299.4220	$1,299.41	$1,299.40	$1,299.50