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	$133.59	11.559%	$149.0317	$149.03	$149.05	$149.00
Purchase #2	$38.88	11.523%	$43.3601	$43.36	$43.35	$43.40
Purchase #3	$30.65	10.588%	$33.8952	$33.90	$33.90	$33.90
Purchase #4	$106.46	11.601%	$118.8104	$118.81	$118.80	$118.80
Purchase #5	$113.90	11.354%	$126.8322	$126.83	$126.85	$126.80
Purchase #6	$92.40	9.132%	$100.838	$100.84	$100.85	$100.80
Purchase #7	$109.72	9.625%	$120.2806	$120.28	$120.30	$120.30
7 purchase totals =	$625.60		$693.0482	$693.05	$693.10	$693.00