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	$123.74	3.383%	$127.9261	$127.93	$127.95	$127.90
Purchase #2	$86.78	13.331%	$98.3486	$98.35	$98.35	$98.30
Purchase #3	$184.76	13.301%	$209.3349	$209.33	$209.35	$209.30
Purchase #4	$34.32	12.826%	$38.7219	$38.72	$38.70	$38.70
Purchase #5	$101.40	10.560%	$112.1078	$112.11	$112.10	$112.10
Purchase #6	$24.64	10.526%	$27.2336	$27.23	$27.25	$27.20
Purchase #7	$13.79	7.304%	$14.7972	$14.80	$14.80	$14.80
7 purchase totals =	$569.43		$628.4701	$628.47	$628.50	$628.30