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	$66.81	10.531%	$73.8458	$73.85	$73.85	$73.80
Purchase #2	$112.28	4.704%	$117.5617	$117.56	$117.55	$117.60
Purchase #3	$119.90	6.686%	$127.9165	$127.92	$127.90	$127.90
Purchase #4	$45.67	11.619%	$50.9764	$50.98	$51.00	$51.00
Purchase #5	$162.60	7.159%	$174.2405	$174.24	$174.25	$174.20
Purchase #6	$52.87	7.710%	$56.9463	$56.95	$56.95	$56.90
Purchase #7	$127.82	3.186%	$131.8923	$131.89	$131.90	$131.90
7 purchase totals =	$687.95		$733.3795	$733.39	$733.40	$733.30