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	$151.33	11.138%	$168.1851	$168.19	$168.20	$168.20
Purchase #2	$22.73	12.147%	$25.491	$25.49	$25.50	$25.50
Purchase #3	$123.85	3.806%	$128.5637	$128.56	$128.55	$128.60
Purchase #4	$84.31	12.221%	$94.6135	$94.61	$94.60	$94.60
Purchase #5	$155.99	11.537%	$173.9866	$173.99	$174.00	$174.00
Purchase #6	$58.48	5.525%	$61.711	$61.71	$61.70	$61.70
Purchase #7	$126.47	3.861%	$131.353	$131.35	$131.35	$131.40
7 purchase totals =	$723.16		$783.9039	$783.90	$783.90	$784.00