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	$142.89	7.400%	$153.4639	$153.46	$153.45	$153.50
Purchase #2	$40.86	6.170%	$43.3811	$43.38	$43.40	$43.40
Purchase #3	$39.30	11.691%	$43.8946	$43.89	$43.90	$43.90
Purchase #4	$69.74	3.394%	$72.107	$72.11	$72.10	$72.10
Purchase #5	$88.55	5.321%	$93.2617	$93.26	$93.25	$93.30
Purchase #6	$125.51	12.269%	$140.9088	$140.91	$140.90	$140.90
Purchase #7	$78.53	3.171%	$81.0202	$81.02	$81.00	$81.00
7 purchase totals =	$585.38		$628.0373	$628.03	$628.00	$628.10