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	$125.62	13.346%	$142.3852	$142.39	$142.40	$142.40
Purchase #2	$132.54	13.773%	$150.7947	$150.79	$150.80	$150.80
Purchase #3	$138.44	4.847%	$145.1502	$145.15	$145.15	$145.20
Purchase #4	$78.49	13.721%	$89.2596	$89.26	$89.25	$89.30
Purchase #5	$31.58	12.450%	$35.5117	$35.51	$35.50	$35.50
Purchase #6	$45.64	4.441%	$47.6669	$47.67	$47.65	$47.70
Purchase #7	$205.85	4.331%	$214.7654	$214.77	$214.75	$214.80
7 purchase totals =	$758.16		$825.5337	$825.54	$825.50	$825.70