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	$150.96	3.304%	$155.9477	$155.95	$155.95	$155.90
Purchase #2	$224.88	7.288%	$241.2693	$241.27	$241.25	$241.30
Purchase #3	$108.98	3.495%	$112.7889	$112.79	$112.80	$112.80
Purchase #4	$58.85	9.561%	$64.4766	$64.48	$64.50	$64.50
Purchase #5	$103.60	7.754%	$111.6331	$111.63	$111.65	$111.60
Purchase #6	$78.84	8.743%	$85.733	$85.73	$85.75	$85.70
Purchase #7	$247.45	7.606%	$266.271	$266.27	$266.25	$266.30
7 purchase totals =	$973.56		$1,038.1196	$1,038.12	$1,038.15	$1,038.10