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	$56.71	13.566%	$64.4033	$64.40	$64.40	$64.40
Purchase #2	$28.82	9.469%	$31.549	$31.55	$31.55	$31.50
Purchase #3	$152.51	12.442%	$171.4853	$171.49	$171.50	$171.50
Purchase #4	$101.28	13.436%	$114.888	$114.89	$114.90	$114.90
Purchase #5	$63.70	8.791%	$69.2999	$69.30	$69.30	$69.30
Purchase #6	$153.91	13.262%	$174.3215	$174.32	$174.30	$174.30
Purchase #7	$85.65	3.488%	$88.6375	$88.64	$88.65	$88.60
7 purchase totals =	$642.58		$714.5845	$714.59	$714.60	$714.50