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	$146.56	12.156%	$164.3758	$164.38	$164.40	$164.40
Purchase #2	$214.98	4.172%	$223.949	$223.95	$223.95	$223.90
Purchase #3	$99.82	8.863%	$108.667	$108.67	$108.65	$108.70
Purchase #4	$179.67	11.590%	$200.4938	$200.49	$200.50	$200.50
Purchase #5	$92.79	4.451%	$96.9201	$96.92	$96.90	$96.90
Purchase #6	$241.53	9.865%	$265.3569	$265.36	$265.35	$265.40
Purchase #7	$74.86	13.818%	$85.2042	$85.20	$85.20	$85.20
7 purchase totals =	$1,050.21		$1,144.9668	$1,144.97	$1,144.95	$1,145.00