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	$63.49	12.711%	$71.5602	$71.56	$71.55	$71.60
Purchase #2	$213.85	7.550%	$229.9957	$230.00	$230.00	$230.00
Purchase #3	$42.88	8.590%	$46.5634	$46.56	$46.55	$46.60
Purchase #4	$235.34	5.757%	$248.8885	$248.89	$248.90	$248.90
Purchase #5	$92.81	9.238%	$101.3838	$101.38	$101.40	$101.40
Purchase #6	$67.66	6.854%	$72.2974	$72.30	$72.30	$72.30
Purchase #7	$56.94	3.715%	$59.0553	$59.06	$59.05	$59.10
7 purchase totals =	$772.97		$829.7443	$829.75	$829.75	$829.90