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	$185.69	3.636%	$192.4417	$192.44	$192.45	$192.40
Purchase #2	$48.78	7.230%	$52.3068	$52.31	$52.30	$52.30
Purchase #3	$29.65	12.851%	$33.4603	$33.46	$33.45	$33.50
Purchase #4	$103.30	9.418%	$113.0288	$113.03	$113.05	$113.00
Purchase #5	$105.63	11.792%	$118.0859	$118.09	$118.10	$118.10
Purchase #6	$46.81	9.633%	$51.3192	$51.32	$51.30	$51.30
Purchase #7	$39.96	7.191%	$42.8335	$42.83	$42.85	$42.80
7 purchase totals =	$559.82		$603.4762	$603.48	$603.50	$603.40