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	$56.82	6.457%	$60.4889	$60.49	$60.50	$60.50
Purchase #2	$14.26	11.175%	$15.8536	$15.85	$15.85	$15.90
Purchase #3	$53.45	11.213%	$59.4433	$59.44	$59.45	$59.40
Purchase #4	$153.41	11.280%	$170.7146	$170.71	$170.70	$170.70
Purchase #5	$212.81	4.340%	$222.046	$222.05	$222.05	$222.00
Purchase #6	$142.52	5.377%	$150.1833	$150.18	$150.20	$150.20
Purchase #7	$14.77	7.640%	$15.8984	$15.90	$15.90	$15.90
7 purchase totals =	$648.04		$694.6281	$694.62	$694.65	$694.60