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	$100.70	4.554%	$105.2859	$105.29	$105.30	$105.30
Purchase #2	$24.59	12.779%	$27.7324	$27.73	$27.75	$27.70
Purchase #3	$95.40	11.495%	$106.3662	$106.37	$106.35	$106.40
Purchase #4	$17.63	6.600%	$18.7936	$18.79	$18.80	$18.80
Purchase #5	$59.36	7.133%	$63.5941	$63.59	$63.60	$63.60
Purchase #6	$141.66	11.671%	$158.1931	$158.19	$158.20	$158.20
Purchase #7	$174.86	12.148%	$196.102	$196.10	$196.10	$196.10
7 purchase totals =	$614.20		$676.0673	$676.06	$676.10	$676.10