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	$99.69	5.574%	$105.2467	$105.25	$105.25	$105.20
Purchase #2	$230.72	5.477%	$243.3565	$243.36	$243.35	$243.40
Purchase #3	$16.37	11.832%	$18.3069	$18.31	$18.30	$18.30
Purchase #4	$46.77	5.448%	$49.318	$49.32	$49.30	$49.30
Purchase #5	$40.56	7.826%	$43.7342	$43.73	$43.75	$43.70
Purchase #6	$124.41	5.366%	$131.0858	$131.09	$131.10	$131.10
Purchase #7	$64.39	11.807%	$71.9925	$71.99	$72.00	$72.00
7 purchase totals =	$622.91		$663.0406	$663.05	$663.05	$663.00