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	$52.62	3.204%	$54.3059	$54.31	$54.30	$54.30
Purchase #2	$189.94	4.414%	$198.324	$198.32	$198.30	$198.30
Purchase #3	$163.49	11.789%	$182.7638	$182.76	$182.75	$182.80
Purchase #4	$100.40	13.146%	$113.5986	$113.60	$113.60	$113.60
Purchase #5	$66.91	7.645%	$72.0253	$72.03	$72.05	$72.00
Purchase #6	$55.98	5.818%	$59.2369	$59.24	$59.25	$59.20
Purchase #7	$43.26	5.741%	$45.7436	$45.74	$45.75	$45.70
7 purchase totals =	$672.60		$725.9981	$726.00	$726.00	$725.90